I90 load non image file

http://catrobatgw.ist.tugraz.at:8080/job/Paintroid-custom-branch-test/458/
http://catrobatgw.ist.tugraz.at:8080/job/Paintroid-custom-branch-test/455/

I90: Error dialog on trying to load non image file or from Picasa with Stamptool.
Also: import png now lets to import from all apps which are able to open
image files, not only automatically the gallery.