Got rid of some compiler warnings because of const POD return values. I think it is unlikely that we will ever have return types that are modifiable as rvalue, so I think we can do without that const.
Merge branch 'master' of https://github.com/hmenke/espresso
Merge remote-tracking branch 'upstream/master'
MMM1DGPU skeleton
Mmm1dgpu working
MMM1DGPU force reduction
MMM1DGPU: Proper CUDA block size. Self-destruct if coulomb method is changed.
Merge branch 'master' of github.com:espressomd/espresso
Merge branch 'master' of github.com:espressomd/espresso
Merge branch 'master' of github.com:espressomd/espresso
Merge branch 'master' of https://github.com/espressomd/espresso into mmm1dgpu

Conflicts:
	src/Makefile.am
	src/core/forces.cpp
Make MMM1DGPU work again after b3fdafb9
Merge branch 'master' of github.com:espressomd/espresso
Merge branch 'master' of github.com:espressomd/espresso
Merge branch 'master' of https://github.com/HRZaheri/espresso
Merge branch 'master' of github.com:espressomd/espresso
Make changing MMM1DGPU parameters work
MMM1DGPU fetch current parameters
MMM1DGPU tuning: Can now tune multiple times, don't add to forces
MMM1DGPU: Make sure inter coulomb always returns the current parameters