Improved matplotlib backend
- mathtex
- transparency (Mac OSX only)

Change-Id: I72fae83fc518be4b2457085f20e9f938087d4396
Reviewed-on: https://iffwww.iff.kfa-juelich.de/review/33
Reviewed-by: Josef Heinen <j.heinen@fz-juelich.de>