Fixed wrongly removed debug variables.
p3m: Make sure p3m isn't startet with nonmetallic epsilon and noncubic box. This is not implemented and would result in wront results.
Corrected faulty mesh density calculation in P3M tuning.

Conflicts:

	src/p3m.c
Fixed wrong starting mesh calculation in p3m tuning.
fixed memory leak in lbgpu
lb print_interpolated_velocity now works with only LBGPU
Fixes previous commit with regards to the print_interpolated_velocities
Merge branch '3.1' of github.com:espressomd/espresso into 3.1
Merge pull request #74 from jdegraaf/3.1

Fixes previous commit with regards to the print_interpolated_velocities
Merge branch '3.1'

Conflicts:
	src/maggs.c
	src/p3m-dipolar.c