Adds the missing endpoints for documents, envelopes and
templates supporting file uploads in a singular request.
Also updates frontend components that would use the prior
hidden endpoints.
This PR is handles the changes required to support envelopes. The new
envelope editor/signing page will be hidden during release.
The core changes here is to migrate the documents and templates model to
a centralized envelopes model.
Even though Documents and Templates are removed, from the user
perspective they will still exist as we remap envelopes to documents and
templates.
