Refactor the various contexts

src/main/scala/leon/LeonContext.scala

src/main/scala/leon/genc/CConverter.scala

src/main/scala/leon/purescala/SelfPrettyPrinter.scala

src/main/scala/leon/repair/rules/Focus.scala

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

src/main/scala/leon/synthesis/Rules.scala

src/main/scala/leon/synthesis/Search.scala

src/main/scala/leon/synthesis/SearchContext.scala

src/main/scala/leon/synthesis/SynthesisContext.scala

src/main/scala/leon/synthesis/graph/Graph.scala

src/main/scala/leon/synthesis/rules/ADTInduction.scala

src/main/scala/leon/synthesis/rules/ADTLongInduction.scala

src/main/scala/leon/synthesis/rules/BottomUpTegis.scala

src/main/scala/leon/synthesis/rules/CEGISLike.scala

src/main/scala/leon/synthesis/rules/CEGLESS.scala

src/main/scala/leon/synthesis/rules/EquivalentInputs.scala

src/main/scala/leon/synthesis/rules/Ground.scala

src/main/scala/leon/synthesis/rules/IntegerEquation.scala

src/main/scala/leon/synthesis/rules/IntroduceRecCall.scala

src/main/scala/leon/synthesis/rules/OptimisticGround.scala