Save Image-Crop information for GIF in docx

Issue:-
    1] When MS Office docx file containing cropped image is
       round tripped with LibreOffice 4.2, image looses
       its cropping effect.
Implementation:-
    1] Converted MAP unit, MAP_PIXEL to MAP_100TH_MM using
       PixelToLogic function.
       As for calculating EMU values for XML, we need
       Original Height and Width of an image in
       100thMM(HMM) format.
    2] Written Export Unit Test (GIF) to verify cropping parameters.

Conflicts:
	sw/qa/extras/ooxmlexport/ooxmlexport.cxx
Reviewed on:
	https://gerrit.libreoffice.org/6595

Change-Id: I54d7b08c96608a0cfca3c2f8833684c09848351c