Fix ConnectionHandler check.

Comparing an Optional to a Connection doesn't really work.

Fix a couple of tests.

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.

In the process, fixed two issues:

- channel who plugin was sending way too many requests - each
  connection was querying every channel in the client. i.e.,
  with 5 servers open there'd be 5 WHOs per channel...

- ServerFrame stops itself listening when *any* frame is closed.
  So closing a channel window then reconnecting wouldn't offer
  an SSL dialog, because it's already unbound the listener.

Issue DMDirc/DMDirc#662

Random test tidying.

Support for core changes.

Fix date format when showing errors.

Closes DMDirc/DMDirc#661

Handle core date API changes.

Update gradle to 2.11.

Update DMDirc repo to HTTPS.

Convert events to use new date APIs.

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

Update plugins after core event changes.

Separate InputModel functions from FrameContainer.

Remove input methods from WindowModel.

Migrate all users to using the InputModel.

Remove FrameContainer parent/child fields.

Remove usages of FrameContainer window methods.

These will be going away shortly.

Remove unused methods/fields.

Migrate DCC plugin to use events.

Migrate debug plugin to showOutput/showError.

Remove unused method.

Use events for some more plugin outputs.

This slightly changes how the logging plugin history window
works - instead of parsing dates and using DMDirc timestamps,
it just shows the logged timestamp like the backbuffer does.

As history tends to span several days this seems more useful.

Issue DMDirc/DMDirc#426

Fix systray plugin

Use events for raw data in/out.

Systray plugin was attempting to set the visibility of the main
window on the EDT, do this off the EDT.

Issue DMDirc/DMDirc#426

Switch some more plugins to use new events.

DMDirc/DMDirc#426

Make logging plugin use new events.

DMDirc/DMDirc#426

Fix some build warnings.