[Review-4-0] Cherry-pick requests

[Muthu Subramanian K]

Hi,

I had recently committed these to the master branch. It would be nice if 
we could have it on the 4.0 branch as well.

PPT Export fix - Autofit of background images
http://cgit.freedesktop.org/libreoffice/core/commit/?id=e481740cc894ea21c8e7a49100d56ca572a21a76

PPTX Import - Flip gradients as well
http://cgit.freedesktop.org/libreoffice/core/commit/?id=abd87f5085267ea514ebd34b23e42fb9b4b6466b

Chart Labels
http://cgit.freedesktop.org/libreoffice/core/commit/?id=228ba082d3148f13eed79e9cdd682953cccaab1c
[This would change the UX a bit, I have explained the changes in a 
little detail in the commit log]

Thanks for the reviews in advance!
Muthu Subramanian