Small fixes.
Merge pull request #183 from HRZaheri/master

fixing some warnings
Added quartic bonded interaction.
Fixed background error collection.
No background errors in tcl.
Fixes
New bond coulomb interaction.
Towards a better Pyhton inteface.
Moved Tcl interpreter into own files.
Shell problem.
Put global variables into System object.
Fixed analyze.
Fix indices in lb_lbfluid_get_interpolated_velocity
Incorporated cellsystem into system.pyx.
Added forgotten file.
Fixed dist.