Unified im/export of rotation at FlyFrame Graphics to
not write their internal old 10th degree format, but to
use deg notation and the correct orientation. Extended
the mechanism to use tooling (SdXMLImExTransform2D) to
completely read/write 'draw:transform' statements. Added
quite some comments due to stuff in the old mechanism(s)

Change-Id: I7d265c1a05532a0dd9b921e383c10b477b4c8846
Reviewed-on: https://gerrit.libreoffice.org/47335Tested-by: Jenkins <ci@libreoffice.org>
Reviewed-by: Armin Le Grand <Armin.Le.Grand@cib.de>