Version update checker

[crazysnailboy]

Implement an check to alert users when new versions of the mod become available.

• For 1.8+, Forge provides native functionality to accomplish this. This is not present for 1.7 however. A single solution which works for all versions may be preferable.
• Would need to correctly differentiate between alpha, beta and release versions.
• The option should be provided in config to disable this, and also to specify whether the user wants to be notified about different types of release.

[crazysnailboy]

I went with a custom solution for 1.7.10, based off of Jabelar's Making A Mod Version Checker tutorial but adapted so that instead of a single line plain text file, it reads the same JSON schema which LexManos implemented for native version checks in Forge for Minecraft 1.8+.

The user can configure whether the update check is performed, and whether they get notified if a new version is found, or a new recommended version. The notification occurs in the form of a clickable chat message when they first enter the game.

For the 1.8+ versions, the built-in Forge version checker notifies users that an update is available for one or more of their installed mods by changing the icon on the mods menu before the player loads the world.