Moved Jsval into Common.Js. Added Progress classes

* Common.Progress now contains not only the still-not-finished
  ProgressNormalizer code, but also some simple classes and interfaces
  for adding DOM-inspired progress events to other classes.

* Renamed Common.Extenders to Common.Extensions (and Extender to
  Extension in all of the classes therein).

* Renamed ListCompare to Equals, and made all of them extension
  methods. Moved one stranded Equals function which did the same
  thing into the same namespace as the others. Similarly
  moved DictionaryCompare.

* Added proper Base64-encoding, and tests for it. Also added
  BCrypt-style Base64 encoding (but no tests for that yet).

Version changed to 0.4.4.4