Additional radian based angle/rotation methods.
remove unncessary degree/radian conversion value from Matrix3
Normalize before getting rotation, fixes #820
Merge commit 'refs/pull/1267/head' of https://github.com/libgdx/libgdx into various
Remove MathUtils.RADIANS/DEGREES, closes #1267
Merge pull request #1318 from xoppa/various

Various math changes and fixes