Ability for an admin to rename offensive displaynames

[matrixbot]

Created by @ matthew:matrix.org.

[ara4n]

Actually, i think we can do this by redactions on a per-room basis. Would be good to be able to do it serverwide though.

[kethinov]

What about renaming people/rooms locally only? (e.g. changes visible only to me.)

e.g. suppose my friend Jon names himself, "His Excellency Lord Jon of Burns, the Wise and Stately Patriarch," I may not have a problem with him choosing to present himself to others using such pretentious honorifics, but it might be nice to shorten his name to "Jon" locally only for my own consumption.

Also generally I've found less technical people don't bother with setting display names, so it would be nice to be able to set them locally so I don't have to memorize their usernames.

[j-maas]

What @kethinov suggests is tracked in #725.