According to the Qt naming policy, methods that return value(s) via
the mutable parameter(s) should have "get" prefix to mention that.
[ChangeLog][QtGui][QQuaternion] Added methods to convert a quaternion
to/from Euler angles and to/from rotation matrix.
Change-Id: I95704e1f4623dc4ca54cd237ea203539fb60d452
Reviewed-by: Sean Harmer <sean.harmer@kdab.com>