remove hangover debug message from internal solver
fixing testcase that is only activated with DLV
another forgotten fix to the testcases (caused by e76abd)
experiments with a new grounding strategy
fix a bug with strong negation in explicit FLP check
cleanup and refactoring in liberal safety implementation
fix a bug in grounder for liberally safe programs
some changes in GringoGrounder
greedy heuristics fine tuning
fix a bug in greedy heuristics
move liberal safety implementation to BaseModelGenerator