Performance regression fix for heap subsumption and invalidity
heuristic. Reintroduced normalisation for heaps.
Merge branch 'master' of https://github.com/ngorogiannis/cyclist

Conflicts:
	src/seplog/sl_deqs.ml
	src/seplog/sl_ptos.ml
	src/seplog/sl_rules.ml
	src/seplog/sl_seq.ml
	src/seplog/sl_seq.mli
	src/seplog/sl_tpreds.ml
	src/seplog/slinit.ml
SL prover now does an invalidity pre-check to the given sequent.
Added of_string function to defs. Added basepair minimisation.