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.
Adds the ability to specify an optional signing order for documents.
When specified a document will be considered sequential with recipients
only being allowed to sign in the order that they were specified in.
David Nguyen
Ephraim Duncan