Jubjub EdDSA

[HarryR]

This introduces the following new gadgets:

• EdDSA_Verify
• field2bits_strict
• PedersenHashToBits

Additionally this branch:

• fixes build problems on OSX.
• Adds Point::as_VariablePointT
• Cleanups to Cmake build system, requiring no modifications when adding files
• Adds libcrypto as a base library to ethsnarks_gadgets

There is one unit test which needs fixing before this can be merged, as it's preventing EdDSA verification from completing.

Additionally the Python implementation of pedersen_hash_zcash is slow, as it multiplies the base point for every bit, rather than the faster double & add algorithm.

[HarryR]

NPM is failing on Travis-OSX. But it's working on my mac... The reason it's failing is:

OK
npm install
npm WARN deprecated circular-json@0.3.3: CircularJSON is in maintenance only, flatted is its successor.
npm WARN deprecated fs-promise@2.0.3: Use mz or fs-extra^3.0 with Promise Support
npm WARN deprecated tar.gz@1.0.7: ⚠️  WARNING ⚠️ tar.gz module has been deprecated and your application is vulnerable. Please use tar module instead: https://npmjs.com/tar
npm ERR! Cannot read property 'match' of undefined
npm ERR! A complete log of this run can be found in:
npm ERR!     /Users/travis/.npm/_logs/2018-11-22T19_06_55_037Z-debug.log
make: *** [node_modules] Error 1
The command "make test" exited with 2.

This looks like some kind of internal npm error and it doesn't get to the real install part...