cut implementation
Merge branch 'master' into infer-cut
Merge branch 'prover' into infer-cut
fv non-exhausting pattern
refuteRigid removed as unused
Merge branch prover into infer-cut
cases of refuteRec reduced as cases of derive
Merge branch 'prover' into infer-cut

Conflicts:
	src/prover/Infer.hs
Merge branch 'prover' into negation
proving negation
Merge branch 'prover' into negation
threecolors example
Merge branch 'prover' into negation
Merge branch 'prover' into negation
derive and neg_derive
Infer.hs: neg_derive
Symmetric definition of neg_derive and derive
neg_derive exists case
neg derive and reduce exist
infer reduce exists