Engine cleanup: move legacy code and delete temp files

Based on our discussion, this pull request did some engine cleanup:
  * Move ``ProtoCore\Parser\Associative`` and ``ProtoCore\Parser\Imperative`` folder to ``src\Legacy``
  * Move ``ProtoAssociative\DependencyPass`` folder to ``src\Legacy``
  * Delete some temporary files which were mistakenly added (e.g., some ``.pidb`` files)
  * I also clean ``ProtoScript`` project. 

@lukechurch , @junmendoza , please review the change.