Move Option to lang.Option, add Map.get/getOrElse/+

doc/purescala.rst

library/lang/Map.scala

library/lang/Option.scala

src/main/scala/leon/frontends/scalac/CodeExtraction.scala

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

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

src/main/scala/leon/utils/Library.scala

...esources/regression/frontends/passing/ImplicitDefs2.scala

...gression/verification/purescala/valid/MapGetOrElse2.scala

...ces/regression/verification/purescala/valid/MapPlus.scala

testcases/repair/Parser/Parser.scala

testcases/repair/Parser/Parser1.scala

testcases/repair/Parser/Parser2.scala

testcases/repair/Parser/Parser3.scala

testcases/repair/Parser/Parser4.scala

testcases/repair/Parser/Parser5.scala