Create a backup every time a font is saved

Merge branch 'master' of github.com:johanmattssonm/birdfont

Merge ../birdfont-2.x

Merge ../birdfont-2.x

Fix hanging export and notification crash bug

White space fixes

Draw filled open paths
This commit moves recalculate_linear_handles to the Path class in order
to set handle position for end points.

Merge branch 'master' of github.com:johanmattssonm/birdfont

Merge branch 'stoptask'

Add button for stopping background tasks

Make all tasks cancelable

Merge branch 'master' of github.com:johanmattssonm/birdfont

Process stroke in background thread and bug fixes

Display window icon in developer builds

Thread safety
Vala disconnects signals automatically but not in a thread safe way.
This happens when the Task object is destroyed in a background thread.

Create fontconfig cache in a background thread

Merge branch 'master' of gitorious.org:birdfont/birdfont

Speed optimization for path simplification and other improvements