Great Annotation Refactor of 2013

This changes the annotation API to be the same as the node API, sans
a few boolean flags that don't apply. The APIs were different, but
there was really no good reason why, so this makes things simpler for
API users. It also means we'll be able to factor a bunch of things out
because they're now duplicated between nodes, meta items and annotations.

Linear model annotations are now objects with 'type' and 'attributes'
properties (rather than 'name' and 'data'), for consistency with elements.
They now also contain html/0/* attributes for HTML attribute preservation,
which obsoletes the htmlTagName and htmlAttributes properties.
dm.Annotation subclasses take a reference to such an object and implement
conversion using .static.toDataElement and .static.toDomElements just
like nodes do. The custom .getHash() functions are no longer necessary
because of the way HTML attribute preservation was reimplemented.

CE rendering has been moved out of dm.Annotation (it never made sense to
have CE rendering functions in DM classes, this was bothering me) and into
separate ce.Annotation subclasses. These are very similar to CE nodes in
that they have a this.$ generated based on something in the DM; the main
difference is that nodes listen to events and update themselves, whereas
annotations are static and are simply destroyed and rebuilt when they
change. This change also adds whitelisted HTML attribute rendering for
annotations, as well as class="ve-ce-FooAnnotation" attributes.

Now that annotation classes produce real DOM nodes rather than weird
objects describing HTML tags, we can't generate HTML as a string in
ce.ContentBranchNode anymore. getRenderedContents() has been rewritten
to be much more similar to the way the converter renders annotations;
in fact, significant parts of it were copied from the converter, so that
should be factored out in the future. This change actually fixes an
annotation rendering discrepancy between ce.ContentBranchNode and
dm.Converter; see the diff of ve.ce.ContentBranchNode.test.js.

ve.ce.MWEntityNode.js:
* Remove stray property

ve.dm.MWExternalLinkAnnotation.js:
* Store 'rel' attribute

ve.dm.TextStyleAnnotation.js:
* Put all the conversion logic in the abstract base class

ve.dm.Converter.js:
* Also feed annotations through getDomElementsFromDataElement() and
  createDataElement()

ve.dm.Node.js:
* Fix undocumented property

ve.ce.ContentBranchNode.test.js:
* Add descriptive messages for each test case
* Compare DOM trees, not HTML strings
* Compare without all the class="ve-ce-WhateverAnnotation" clutter

ve.ui.LinkInspector.js:
* Replace direct .getHash() calls (evil!) with ve.getHash()

Bug: 46464
Bug: 44808
Change-Id: I31991488579b8cce6d98ed8b29b486ba5ec38cdc