Create an administrative tool allowing us to update our stored version of a document title

What to do:
Create a tool for Hypothesis admins that will allow us to change the doc title stored in `document`.`title`.

Why:
Conversation here: https://hypothes-is.slack.com/archives/C2BLQDKHA/p1590410846427200

An annotation on a page that has an incorrect rel=canonical or similar tag can forever create a document title that is incorrect in Hypothesis, even if the HTML is fixed later.

Start by locating the code that stores documents and the administrative tooling entry points, then trace how `document`.`title` is populated. Define the admin workflow for changing the stored title and verify that the persisted title changes without altering unrelated document data.

Written by the indexing model from the issue text.