Several improvements in preparation for the new backends.
- Removed duplicated methods fromBoolean, fromAPSInt, fromInt and fromAPFloat. The methods mkBoolean, mkBitvector and mkFloat are now used instead.
- The names of the functions that convert BVs to FPs were swapped (mkSBVtoFP, mkUBVtoFP, mkFPtoSBV, mkFPtoUBV).
- Added a couple of comments in function calls.
- Changed how constraints are encoded in the refutation manager so it doesn't start with (false OR ...). This change introduces one duplicated line (see file BugReporterVisitors.cpp, the `SMTConv::getRangeExpr is called twice, so I can remove this change if the duplication is a problem.