Libgdx rendering: Missing features

[coldwarrl]

This is just a collection of missing libgdx features, which could be implemented to be feature complete with the Swing implementation:

• modifiers (e.g. texture modifiers)
• are graphical tilesets fully implemented ?

[coldwarrl]

Just as remark: It should also be considered if not https://www.lwjgl.org/ shall be the main render target for Zircon. An openGl implementation seems not that difficult and maybe more stable and reliable as a libgdx target iin the long run...