Added generic TheoryEncoders to Leon

src/main/scala/leon/Main.scala

src/main/scala/leon/codegen/runtime/Monitor.scala

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

src/main/scala/leon/evaluators/StreamEvaluator.scala

...scala/leon/invariant/engine/UnfoldingTemplateSolver.scala

src/main/scala/leon/laziness/FreeVariableFactory.scala

src/main/scala/leon/laziness/LazinessUtil.scala

src/main/scala/leon/laziness/LazyClosureConverter.scala

src/main/scala/leon/laziness/LazyClosureFactory.scala

src/main/scala/leon/purescala/Definitions.scala

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

src/main/scala/leon/purescala/Extractors.scala

src/main/scala/leon/purescala/TreeTransformer.scala

src/main/scala/leon/purescala/TypeOps.scala

src/main/scala/leon/purescala/Types.scala

src/main/scala/leon/solvers/SolverFactory.scala

...cala/leon/solvers/combinators/Z3StringCapableSolver.scala

src/main/scala/leon/solvers/cvc4/CVC4UnrollingSolver.scala

...in/scala/leon/solvers/smtlib/SMTLIBQuantifiedTarget.scala

src/main/scala/leon/solvers/smtlib/SMTLIBSolver.scala