Further moderation requests

[gravitystorm]

I've had requests to make the following possible for moderators:

• hide changeset tags (this is complex since they are replicated, perhaps more similar to redactions than normal moderation)
• hide or modify diary entries and comments under them (PR created)
• hide comments on notes (we can hide a note fully but if only one of 20
  comments is obnoxious we have to hide the full note and re-create it
  minus the obnoxious comment)
• modify an obnoxious user name or avatar
• hide or modify a user's profile page

Some of these can be "just done", others will need to be logged separately as larger projects.

[gravitystorm]

• Block signups for variant emails, from users that have already been blocked. This will require storing the canonical email, and during signup check for existing signups with the same canonical email that have blocks against them.

[SomeoneElseOSM]

Currently moderators have no control over an account's display name. Users (even blocked users) can change their display name. In addition to "modify an obnoxious user name" in the list above we'd need to prevent a blocked user from changing it back (or to something else).

[woodpeck]

Just as an extra data point to the above: Within the last couple weeks there have been three different requests to DWG from different people (on different continents) which had similar characteristics:

• someone had made a very local change (e.g. added just one house)
• the change was described in the changeset comment ("added my house")
• the user did not realize that the changeset comment would be public, and now felt that we were leaking personal data about them.
  In these cases, even when we redact the actual changed objects, the changeset comment remains linked to the user, as does the - relatively small - bounding box. To fully solve this kind of problem, we'd either have to be able to suppress the changeset comment and bbox, or perhaps suppress the changeset altogether.
  Currently the only remedies available in these cases are to either have an admin manually fiddle with database contents (bad), or have an admin delete the user account which will at least disconnect the edit from the user name - still it isn't perfect as the changeset comment could well allow identifying an individual, and at the same time it is quite the nuclear option.