New PNG encoder that supports compression, more efficient vertical flipping, and minimal allocation when encoding multiple PNGs.

closes #2501
Fixed PNG encoder for all pixmap formats.

#2501
Fixes #2512
Better way of specifying initial buffer size.
Added renderObjects() to TiledMapRenderer
Removed IOException, reset pixel buffer position.
Fixes #2517
Add MeshBuilderTest; normalTransform should be Matrix3; use color to tint specified vertex colors.
Use IntMap to store pointer against pointer UUID. Fixes #2516
Label#setEllipse -> Label#setEllipsis.

closes #2529
correct color scaling in vertex shader
Add null check in BitmapFont#toString()

BitmapFont loaded from FreeTypeFontGenerator does not have a fontFile set.

Fixes #2510
Removed unnecessary code