* Bump Scala versions
Support Scala 2.12.9
and 2.13.0.
To make this easier, we delete the `scripts` project. Everything
that was in here was covered by content on the website. We also
delete the `doc` folder, as that was a remnant from when `scripts`
was called `doc`.
* Crib uPickle akka-http support while we wait for publish
* Fix compiler warnings
* Add note on test logging to contribution guide
* Reduce duplication in Blockchain implementation
* Use Scala 2.12 for website
* Introduce compat package object for collections converters
* Fix Either compiler warnings
* Add sync-chain and create-wallet docs from deleted scripts
* Fix rebase goofup
- 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
