Support renaming a user, local only (user aliases)

[matty-r]

This would help when a user is accessing via a bridge - we can "rename" or "tag" a user with a different nick, which can be used for mentions etc

[matty-r]

Moved to v0.6.0

[matty-r]

Potential options

• [ ] 'Current Session'. When the app is closed it will drop the alias.
• [ ] 'Current nick only'. If the user renames themselves or leaves, it will drop the alias.
• [ ] 'Room' only. Only apply to nick in current room.
• [ ] 'Global', applies across the entire server.
• [ ] 'Conditional', if nick = 'something' and line starts with 'somethingelse'

[matty-r]

Move to v1.0.0. This is a pretty big task that will require setting up processing a line after it's formatted