fgl implements Show for Patricia trees from 5.5.0.0 on
Merge branch 'ShowGraph' into develop
Give strategy the opportunity to return hints (aka counterexamples)

This comes in handy, if the user wants to analyse why an induction
cannot prove or disprove a property
Generate hints if k-induction fails within given depth

This required the change of the interface of Strategy to allow
returning 3-valued results that may include hints.
Improve code layout
Use hints feature in examples
Instance of MonadSMT for WriterT
Removed dead (commented) code
Merge branch 'GenCounterEx' into develop