EnumerationSolver/Portfolio extends Incremental+Assumption

src/main/scala/leon/solvers/EnumerationSolver.scala

src/main/scala/leon/solvers/NaiveAssumptionSolver.scala

...main/scala/leon/solvers/combinators/PortfolioSolver.scala

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

src/main/scala/leon/synthesis/SynthesisOptions.scala

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

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