Evince

The Read activity and other components in Sugar that display PDFs use evince for that.

These tickets track the effort to upstream the changes we had to do:

• Add python bindings for libevince
• Add evince_embed_init so embedders can init threads and evince internals

Done

• Make EvDocumentInfo and friends GTypes
• Make EvJobPriority a proper GType
• move reusable code into a shared library so other apps can display documents using evince code
• Expose ev_view_set_zoom_for_size for embedders to use