fdo#65833 Fix to preserve VML Canvas Information

Grab-bagged the "editas" attribute of v:group and added UT for
the same

Please verify this fix on MS Office 2007 as it renders the mc:Fallback VML part

Conflicts:
	sw/qa/extras/ooxmlexport/ooxmlexport.cxx
Reviewed on:
	https://gerrit.libreoffice.org/7335

Change-Id: I4e4456997621089967514009005ee775b71d6d69