Currently I implemented it with opacity, but I'm sure a designer
could do a better job.

In Ext4 each event handler will receive an additional options argument
that was given in the addListener method.  To make this clear, we
automatically append this extra parameter to each event.

- Separated out two events: showClass and showMember.
- The showMember now also gets fired when navigating to a member
  within one class.
- All the tracking events are now fired *after* the thing has happened.
  That's the common practice in ExtJS and also useful when something
  goes wrong in the event handler.
- Added documentation.
- Cleaned up trailing whitespace.

Again, use classname instead of ID for styling.

Also Docs.Favorites no more calls for some global treePanel component,
but is instead given the TreePanel it should use.

No more access ClassOverview by ID. Instead it just has a classname
which is also used for styling in CSS.

The tab panel no more uses an ID.

Created separate store for Docs app settings to remember that.

Allows to avoid duplication of doc-comments when one class aliases
methods from other class.

Solves the problem of --append-html not being correctly escaped.

Might be better to have a separate section for static methods, but
for now it's better than nothing at all.

When using Ext.define and not having {extend: "SomeClass"} or
@extend SomeClass, then automatically assuming that we're extending
Ext.Base.

Visually marking them as protected with label similar to deprecated.

For History/Favorites it replaces the MenuButton, which duplicated
a lot of functionality in HoverMenuButton.

I didn't know that an additional event options object gets passed
to each event handler.

Now we have all our dependencies loaded dynamically.