Abide verification framework

First internal release of the abide framework that features:
- reflective rule and analyzer loading
- abide compiler plugin
- basic cli that provides 4-phase compilation with abide on top
- sbt plugin sketch (needs version management)
- traversal analyzer that applies single-traversal rules
- scoping analyzer that applies single-traversal rules and provides scoping and/or path information
- a few example rules and doc on how to add more

Do you have enough performance margin? As you noted above, a cold JVM might need quite a lot more time to jit-compile than in a usual run. I am afraid these tests might prove flaky at some point.

My suggestion would be to have a performance test suite, and run that separately. Also, a number of "warmup" runs for each case should be part of the test setup.