This avoids the confusion of having a property called panel that
refers to an instance of Bridge.

This prevents other objects reaching in and calling methods further
down the chain. If a method needs to be called then it should be
proxied by the Guest object.

Unclear why it's needed, might be used for file:// endpoints...

* Now throw an error if startDiscovery is called twice.
* Throw an error if two server instances message each other.
* Remove the context of the onDiscovery callback.

* Remove the jQuery dependency.
* Pass in window as an argument to the constructor.
* Move defaults off the prototype and onto the constructor fn.

We nullify the default options to ensure that no objects can be shared
between instances and remove the no-op onConnect callback.

This was fixed by 8e1c52f7 and moving bootstrap into app.coffee

The current implementation assumed that the setupAnnotation method
needed to do a large amount of work and so batched the calls. Our
sidebar no-ops this method so we can effectively get rid of the
setup method and batch calls.

This has been replaced with the crossframe service and related modules,
we still have the AngularAnnotator class for the auth service to
hook into but this is little more than a shell now.

This has now moved to the threading service.

This keeps bootstrapping functions in one place and makes it much easier
to disable such calls in the test environment. The check currently
uses the mocha global variable, in future it would be nicer to have
an APP_ENV flag or similar defined before the tests run.

This causes really hard to track down errors when $digest is called. In
reality though this still needs a more robust fix.

The idea is to keep bridge and discovery code agnostic of the
application.

This makes it easier to provide consistent interface between the
annotator event system and the angular one.