Only one place in the core needs the silly IRC format, so just
inline it there.

This is fairly trivial to implement with streams/lambdas,
no need to have our own hand-rolled list implementation
for it.

Fixes #521
Fixes #522

This will go in a plugin instead.

Think we're going to stop supporting this. If there's a decent
case for it then it should be done as a DisplayProperty instead.

(This depends on a plugins change)

Fixes #500

These are just proxies to ChannelInfo for now.

Add more verbose messages.

This just provided default implementations of most of the
ReadOnlyConfigProvider interface, which as of J8 we can
now just put in the interface itself.

DisplayableError is now mutable and not an autovalue.
CoreErrorsDialog now stores errors and updates them appropriately.

Fixes DMDirc/Plugins#319

Fixes #472