Solver-based enumerator, varies size of models to get interesting tests

src/main/scala/leon/datagen/SolverDataGen.scala

...main/scala/leon/solvers/combinators/UnrollingSolver.scala

src/main/scala/leon/synthesis/ExamplesBank.scala

src/main/scala/leon/synthesis/ExamplesFinder.scala

src/main/scala/leon/synthesis/SynthesisPhase.scala

src/main/scala/leon/synthesis/Synthesizer.scala

src/main/scala/leon/utils/FreeableIterator.scala

src/main/scala/leon/utils/ModelEnumerator.scala