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 github.com:espressomd/espresso
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 github.com:espressomd/espresso
Merge branch 'master' of https://github.com/HRZaheri/espresso
Merge branch 'master' of github.com:espressomd/espresso
LEes Edwards with dynamic rebuild of comms.
Lees-Edwards docs
ELC+MMM2D: Const. potential feature + Fixes for diel. contrast -1 -1
Merge branch 'master' of github.com:espressomd/espresso
Fixed wrong file name in ug.
Distclean myconfig-sample.hpp
Merge branch 'master' of github.com:espressomd/espresso
Mmm1dgpu: move mpi.h dependents into a separate cpp file not compiled using nvcc.

This solves the issue that nvcc does not find mpi.h.
Integrated MMM1D_GPU into jenkins config files.
Some fixes to the compilation docs.
Moved field output of capacitor-freature to mmm-common, added documentation
Registered field-output command