* Refactor decoding in compiler
* remove obsolete comment
* factorize -decodeLf2Version and decodeLf1Version
* call the right decodeScenarioModule depending on the target LF version, update incremental build tests
* split encoding into two modules, call the right encodeScenarioModule in writeDalfFile
* delegate to EncodeV2.hs in Encode.hs
* remove noisy type signature, was there initially to guide me but I think it adds more confusions than it clears up things
