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

Yeah, these were just sanity checks during optimizer macro tweaking. The speedup is actually much higher than 2x so the test hasn't failed for a while I believe. I'm generally more interested by the reporting during the test than the actual test itself.

I would also be in favor of a real performance test suite (with more concrete comparison examples), but I don't really now about performance testing so I didn't look into it that much. Most resources I found were very focused on testing small parts of the program whereas traversals need to be of a certain size for a performance gain to be visible.