add Affine2 matrix, optimize scene2d group transform
GWT compatibility; name change
Added Cell#clearActor
Added test cases, removed confusing getScale/getRotation

Reducing matrix to original components depends on concatenation order.
Something like decomposeRotScl() & decomposeSclRot() could be added
instead, but does anyone need it?
Fixes #2342
Update CHANGES
Added combinations for convenience.
Setter for tap square size.
Better parameter name.
Removed Actor#setCenterPosition, added setPosition(x,y,align).

Related: ac4ced584cae20252c8a420a6a654a1bc52dcfcf
Added setExecutable.

closes #2344
Merge remote-tracking branch 'origin/master'
JsonReader, forward slash added to characters an unquoted strings cannot start with.

closes #2361
Merge pull request #2330 from vmilea/affine

add Affine2 matrix, optimize scene2d group transform
Stage JavaDoc correction.
Merge pull request #2363 from nooone/stagejavadoc

Stage JavaDoc correction.
updated native build to iOS 8.0 SDK
Merge branch 'master' of https://github.com/libgdx/libgdx
Merge branch 'iap' of https://github.com/libgdx/libgdx
Delete gdx-setup.jar