Merge pull request #51 from bbarker/master

"nearly working" gurobi interface
Updating: adding more example in PCPV/EXTERN
Updating: working on PCPV/EXTERN
Updating: more work on PCPV/EXTERN
Updating: work on FALCON and PCPV/EXTERN
Updating: more work in FALCON
Updating: PCPV/EXTERN: infseq -> stampseq
Updating: improving PCPV/EXTERN
Updating: improving PCPV/EXTERN
Updating: improving FALCON
Updating: adding list_vt to PCPV/EXTERN
mainly adding prototype for cnfize for a list of grexps