libsnark

Use gstew5's fork of ate-pairing, which turns on -fPIC in SUPPORT_SNARK=1 mode

Change some includes to allow dependent programs to build out of place.

Fix a typo in include path; this closes #7.

Add an implementation of a zk-SNARK for multi-predicate PCD, based on [CTV15].

Extend compliance predicate interfaces and PCD tally example to provide information about accepted input types.