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.

Move gradle scripts into gradle/

shutdown executor on frame close.

Stop thread bombing when typing.