Add Multipart to replace Mutliparse

My reasoning behind this stems from a few issues. The Multiparse system is setup to URL Decode as well as Form Data parsing. However, the URL Decoding is already being performed by the Router.standardPreparation() method. There should not be dual code for this purpose. Second, the Multiparse.Multipart class had scoping issues from previously being done in es5. This class re-implements the functionality but flattens Multiparse and Multiparse.Multipart into a single class. This makes the event emission easier. The overall scoping is now tighter and there is no hoisting of this into self or that.

Docs and tests are still missing.