Add scalav 2.12.7 to the travis ci matrix
Add more jdk versions
explicitly set scalav when starting sbt for travis
Bump junit interface for secp256k1 tests
remove openjdk/oraclejdk 9 for now
- separate Java source copied from libsecp256k1 into separate module
- split main module into core core-gen core-test
- generators can be published separated to core code for use in
3rd-party tests
- code coverage needs to be aggregated
