Update matplotlib backend

- Add all formats that matplotlib can export
- Add internacionalization support for matplotlib
- Add paper-background support

TODO

- Check PO files
- Fix background support

  Take a look in [this
  demo](http://matplotlib.org/examples/pylab_examples/color_demo.html)
  and in [this
  hack](http://stackoverflow.com/a/5181916/1802726).
Remove title for matplotlib

The title **must** be setup in the final document.

Close #86.
Fix the issue with --background for matplotlib
Update PT translation
Merge branch 'update-matplotlib'