Add Ixeris compatibility

[decce6]

This PR adds compatibility with Ixeris mod.

• Added method to PlatformProvider to check whether Ixeris is installed
• Added Main#runOnMainThread, Main#queryFromMainThread and Main#runOnRenderThread, which makes use of the API provided by Ixeris when it is installed

Closes #41 and decce6/Ixeris#51

[decce6]

To explain why this was needed: Ixeris performs events polling on the main thread (the thread which the game is started on) and spawns a second thread as the render thread. Interactions with the native window need to happen on the main thread. Because event polling is done on the main thread, callbacks are invoked there too, instead of on the render thread, which is expected. Ixeris handles these when GLFW is used, and provides the API for mods that use native code.

I made this PR as non-invasive as possible. The interaction with Ixeris API is done completely in Main.java.

[decce6]

I've resolved the merge conflicts and slightly improved performance.