unit, integration, and regression tests can now share code as they are
compiled together.

Unit tests are now in package leon.unit and shared code lives in
leon.test.

- src/test holds unit tests that should be testing one feature alone

- src/integration holds integration tests that can use extraction,
  solvers, codegen, etc..

- src/regression runs all the regression suites.

For those tired of waiting hours for their
test results.

Performance tests are invoked via "sbt perf:test". Currently testing
performance of CEGIS on some random synthesis problems

Refactored the condition abduction code, refactored InSynth code out of Leon, and added the InSynth core library, with substantial amount of fixing and clearning sources, tests, and testcases

Ensures that tests run in an acceptable amount of time.
Needs at least 5 runs. Can cause failures of test-only due to
warm-up and class loading effects.