benchmarking for all kinds of UFS checks if executed
vim modelines
benchmarking parts of propagation
fix a bug in ClaspSolver
deactivated superfluous debugging
just to be on the safe side
rule shifting as done by gringo (who knows perhaps this is more efficient)
in isModel, propagate and check propagation only if no variables are free
Merge branch 'master' into ps

Conflicts:
	src/ClaspSolver.cpp
fixing isModel (commit 650f10acc5 was a bad idea)
skipping certain amounts of propagations
removing superflous comment
making sure that at least one of the two methods is used (there is no further else!)
attempt to fix bb1c10c9523
only resetting propagator when needed

(i.e., if anything nontrivial was done since last reset or if registry has changed)