This paste image patch is based on Victor Saase\'s insert image patch,
with grateful thanks to Victor for making a good start.
This patch is to be applied to a vanilla xournal-0.4.5.
This patch therefore contains Victor\'s changes, and also:
+ images are now stored in the journal file, inline in the XML, as
base64 encoded PNGs.
+ images can be pasted in from the clipboard
+ copy and paste of images works within the application
+ export of image with PDF now works
I also fixed this bug:
+ free pixbufs using g_object_unref not g_free.