## Description
Replace the PDF renderer with an custom image renderer.
This allows us to remove the "react-pdf" dependency and allows us to use
a virtual list to improve performance.
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.
David Nguyen
Ted Liang