TreeGrammarDecomposition: Major bug fixes for instances with n>=2 (i.e. for introducing more than 1 cut). 
Not only the sufficient set of keys was not generated the right way, but also the MinCostSAT formulation was faulty.
Everything fixed and should now work out just fine.
MaxSAT: switched a debug to a trace call, since it is not usually necessary

git-svn-id: http://gapt.googlecode.com/svn/trunk/source@2171 85d21ef8-add0-11de-ae77-5bfb9c5a3f34