Fix HighlightManager not respecting optionals.

Remove BaseConfigProvider.

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

Switch channel away/back to new formatter.

Use new plugin syntax.

Fix broke core errors dialog model.

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

Fixes DMDirc/Plugins#319

Bump raven to 6.0.0.

No major changes, just a version bump for the Sentry protocol
(for Sentry 7) and removal of UDP connections which we never
used.

Add a LoggingExecutorService and use it for sentry error reporting.

Fixes #472

Set up Raven properly.

Add a ProgramErrorAddedEvent to fix some recursive bugs.

Add an interface for FrameContainers.

Fix all errors being not applicable.

Publish nicklist clear events synchronously.

Tidy up some error handling.

Fixes DMDirc/Parser#62

Switch to DisplayableError for the core errors dialog.

Fix users being completely broken.

Switch some more output to events.

Remove Channel from a few commands.

Add a getNickname to Connection.

This should probably be moved to the LocalClient interface when
it exists.

Add a set nickname to Connection.