Implements JsonFilter, deleting user tokens

* Implements JsonFilter filter object. All application/json responses are
	wrapped in a JsonObject, as a measure to prevent XSSI.
* Fully implements listing & revoking user tokens in the profile page.
* Initial half-through-through implementation of a "UserOwned" concept, the
	idea being any model that could be "owned" by a user (Email, Token, Post, etc)
	can extend this class, which specifies the owning userId. This gives these
	objects a shared generic type. We'll see how this pans out.