Remove child event busses.

Closes #662.

Fix HighlightManagerTest.

Add source checks for eventbus handlers.

In preparation for child eventbusses being removed, anything
trying to subscribe to specific windows now needs an explicit
check.

Issue #662

Add a base class for events with a WindowModel source.

For #662, it makes sense to have a standard way to
get the source from events we may wish to filter.

This introduces a SourcedEvent interface, and adapts classes
to use it.

Automatic test tidying.

Remove some unused code.

Switch to new date APIs.

Update gradle to 2.11.

Update DMDirc repo to HTTPS.

Update date handling after parser changes.

The parser now uses the new API too, so we don't need to
do horrible things to convert.

Convert events to use new date APIs.

Java 8 introduces a sane API for dates; to store datettimes
we should now be using LocalDateTime.

Remove some unused code.

Remove unused DisplayableEvent properties.

Now everything is using events, we don't need the legacy
format identifier.

Assorted tidying.

Assign IDs to windows.

This allows windows to be uniquely identified and shared with
clients that are running outside of the DMDirc process (e.g.
a web UI, or a remote instance).

Separate Server and FrameContainer.

Separate InputModel functions from FrameContainer.

Remove input methods from WindowModel.

Migrate all users to using the InputModel.

Introduce a model for window input.

Instead of WindowModel defining lots of methods on the off-chance
that the window is writable, pull them all into a separate
optional InputModel.

For ease of transition, FrameContainer will just implement both,
but eventually the input handling should be pulled out into
its own class.

Remove FrameContainer parent/child fields.

Remove usages of FrameContainer window methods.

These will be going away shortly.

Make the WindowManager track windows.

Despite its name and description, the WindowManager relied on
each FrameContainer having a reference to its parents and all
its children.

The WindowManager now stores this information itself, and so
the FrameContainer methods can be gradually phased out.

Remove ramaining addLine methods.

Closes #426

Add events for sent messages/ctcps/notices/raw lines.

Use events in ShowTopic command.