basic usage of theory encoder for arrays

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

src/main/scala/leon/solvers/RawArray.scala

src/main/scala/leon/solvers/smtlib/SMTLIBZ3Solver.scala

src/main/scala/leon/solvers/theories/ArrayEncoder.scala

src/main/scala/leon/solvers/z3/FairZ3Solver.scala

src/main/scala/leon/solvers/z3/Z3UnrollingSolver.scala