Add the beginnings of Sponge API support, for GH-51

[satoshinm]

Allow running as a plugin for Sponge: https://www.spongepowered.org

[satoshinm]

Added the repo and dep following https://forums.spongepowered.org/t/how-to-setup-maven-with-sponge/4423/2 but it fails to build:

WebSandboxMC $ mvn package
[INFO] Scanning for projects...
[INFO] 
[INFO] ------------------------------------------------------------------------
[INFO] Building WebSandboxMC 1.6.0
[INFO] ------------------------------------------------------------------------
Downloading: https://repo.spongepowered.org/Sponge/maven/org/spigotmc/spigot-api/1.11-R0.1-SNAPSHOT/maven-metadata.xml
[WARNING] Could not transfer metadata org.spigotmc:spigot-api:1.11-R0.1-SNAPSHOT/maven-metadata.xml from/to sponge-repo (https://repo.spongepowered.org/Sponge/maven/): Failed to transfer file: https://repo.spongepowered.org/Sponge/maven/org/spigotmc/spigot-api/1.11-R0.1-SNAPSHOT/maven-metadata.xml. Return code is: 308 , ReasonPhrase:Permanent Redirect.
[WARNING] Failure to transfer org.spigotmc:spigot-api:1.11-R0.1-SNAPSHOT/maven-metadata.xml from https://repo.spongepowered.org/Sponge/maven/ was cached in the local repository, resolution will not be reattempted until the update interval of sponge-repo has elapsed or updates are forced. Original error: Could not transfer metadata org.spigotmc:spigot-api:1.11-R0.1-SNAPSHOT/maven-metadata.xml from/to sponge-repo (https://repo.spongepowered.org/Sponge/maven/): Failed to transfer file: https://repo.spongepowered.org/Sponge/maven/org/spigotmc/spigot-api/1.11-R0.1-SNAPSHOT/maven-metadata.xml. Return code is: 308 , ReasonPhrase:Permanent Redirect.
Downloading: https://repo.spongepowered.org/Sponge/maven/net/md-5/bungeecord-chat/1.10-SNAPSHOT/maven-metadata.xml
[WARNING] Could not transfer metadata net.md-5:bungeecord-chat:1.10-SNAPSHOT/maven-metadata.xml from/to sponge-repo (https://repo.spongepowered.org/Sponge/maven/): Failed to transfer file: https://repo.spongepowered.org/Sponge/maven/net/md-5/bungeecord-chat/1.10-SNAPSHOT/maven-metadata.xml. Return code is: 308 , ReasonPhrase:Permanent Redirect.
[WARNING] Failure to transfer net.md-5:bungeecord-chat:1.10-SNAPSHOT/maven-metadata.xml from https://repo.spongepowered.org/Sponge/maven/ was cached in the local repository, resolution will not be reattempted until the update interval of sponge-repo has elapsed or updates are forced. Original error: Could not transfer metadata net.md-5:bungeecord-chat:1.10-SNAPSHOT/maven-metadata.xml from/to sponge-repo (https://repo.spongepowered.org/Sponge/maven/): Failed to transfer file: https://repo.spongepowered.org/Sponge/maven/net/md-5/bungeecord-chat/1.10-SNAPSHOT/maven-metadata.xml. Return code is: 308 , ReasonPhrase:Permanent Redirect.
Downloading: https://repo.spongepowered.org/Sponge/maven/net/md-5/bungeecord-parent/1.10-SNAPSHOT/maven-metadata.xml
[WARNING] Could not transfer metadata net.md-5:bungeecord-parent:1.10-SNAPSHOT/maven-metadata.xml from/to sponge-repo (https://repo.spongepowered.org/Sponge/maven/): Failed to transfer file: https://repo.spongepowered.org/Sponge/maven/net/md-5/bungeecord-parent/1.10-SNAPSHOT/maven-metadata.xml. Return code is: 308 , ReasonPhrase:Permanent Redirect.
Downloading: https://repo.spongepowered.org/Sponge/maven/org/spongepowered/spongeapi/6.0.0/spongeapi-6.0.0.pom
[INFO] ------------------------------------------------------------------------
[INFO] BUILD FAILURE
[INFO] ------------------------------------------------------------------------
[INFO] Total time: 0.881 s
[INFO] Finished at: 2017-05-20T22:37:22-07:00
[INFO] Final Memory: 11M/258M
[INFO] ------------------------------------------------------------------------
[ERROR] Failed to execute goal on project WebSandboxMC: Could not resolve dependencies for project io.github.satoshinm:WebSandboxMC:jar:1.6.0: Failed to collect dependencies at org.spongepowered:spongeapi:jar:6.0.0: Failed to read artifact descriptor for org.spongepowered:spongeapi:jar:6.0.0: Could not transfer artifact org.spongepowered:spongeapi:pom:6.0.0 from/to sponge-repo (https://repo.spongepowered.org/Sponge/maven/): Failed to transfer file: https://repo.spongepowered.org/Sponge/maven/org/spongepowered/spongeapi/6.0.0/spongeapi-6.0.0.pom. Return code is: 308 , ReasonPhrase:Permanent Redirect. -> [Help 1]
[ERROR] 
[ERROR] To see the full stack trace of the errors, re-run Maven with the -e switch.
[ERROR] Re-run Maven using the -X switch to enable full debug logging.
[ERROR] 
[ERROR] For more information about the errors and possible solutions, please read the following articles:
[ERROR] [Help 1] http://cwiki.apache.org/confluence/display/MAVEN/DependencyResolutionException

I can download https://repo.spongepowered.org/Sponge/maven/org/spongepowered/spongeapi/6.0.0/spongeapi-6.0.0.pom from my browser so not sure why Maven cannot.

[satoshinm]

WebSandboxMC/sponge/WebSandboxSpongePlugin.java:[4,40] package com.sun.javafx.beans.annotations does not exist

[satoshinm]

Current status: the Sponge plugin is able to load, load/save config, and serve the web socket / http server. But the bridges and listeners are Bukkit-specific, not yet ported / factored out. Notes on Bukkit-specific deps:

where	Bukkit	Sponge
BlockBridge	Material, for translation (config as strings, but looked up as Material)	BlockType
BlockBridge	BlockState for metadata wool and sign	BlockState
BlockBridge	Sign for text	DataManipulator
PlayersBridge	Location for coordinates	Location
PlayersBridge, WebPlayerBridge	Entity for sheep	Entity
PlayersBridge	Player for locating other players	Player

[satoshinm]

Since there are a lot of changes/refactoring, although it isn't complete (only runs the ws/http server, no bridging to the world), going to merge this to master to avoid divergence.