Refactor targets

[4e554c4c]

We should refactor how targets are handled throughout the codebase, and give a special type to channels which includes their STATUSMSG prefix and chantype. Some work has been done to parse targets better in #623, but more work is needed to clean up how targets are managed through the codebase.

[tarkah]

Agreed! This will also allow us to handle case mapping much easier since we will have control over how channel / nicks are constructed, which is long overdue.