mostly python updates

- added fusion moves to c++ and python
- fixed bug in lazy flipper visitor specialization
- changed implementation details of ad3 wrapper
- imporved indAndFlip 
- renamed argument in gm::evaluate
- added OPENGM_ASSERT to dynamicp. to check if model is tree (only in debug)
- exported timing visitor to python
- improved numpy-c++ converter
- fixed bugs in python wrapper (in pottsFunctionGenerator and in examples)
- changed parameters of loc
- removed unused headers (lp_inference stuff)
- partially removed external lib. from travis