Squash synthesis conversion phases

src/main/scala/leon/evaluators/RecursiveEvaluator.scala

...in/scala/leon/purescala/CompleteAbstractDefinitions.scala

src/main/scala/leon/purescala/Expressions.scala

src/main/scala/leon/purescala/Quantification.scala

src/main/scala/leon/synthesis/ConversionPhase.scala

src/main/scala/leon/synthesis/ConvertWithOracle.scala

src/main/scala/leon/utils/PreprocessingPhase.scala