Lens/connector scripts

[fanbomeng97]

First prototype of Connector Package (Have created the importable asset package, but the .gitignore configuration file ignored the asset package, so the package is not include in the GiHub)

• Added keyboard to the BaseScene
• Changed the Json parse tool (from Litjosn to SimpleJSON)
• Added scripts for connector package
• Created a demo scene to show how to use the package
• Updated README

To reviewers:

• Don't need to review the SimpleJSON scripts, these are external library
• Before testing the scripts and demo scene, please run HoloRepository UI server, current scripts are developed based on the UI server
• There will be some scripts appear twice, because I copied the connector scripts to the connector folder, you just need to review on of them

[nielsboecker]

I think excluding the AssetPackage from the actual code makes sense. But after we have sorted out this PR, you can create a GitHub release. So it will look kinda like the release page of the MRTK. You can specify a version number (maybe 0.1.0), describe it a bit, and attach the package file there.

[fanbomeng97]

@nbckr I have made some changes based on your comments, you could have a look when you have time