Override Skin::doEditSectionLink

So that in future we can reduce the amount of hacks in editor.js

Also, in the process, change editor hash to #editor/[section] from
 #editor-[section]. This is a more widespread pattern for hash routes,
used e.g. in Backbone.

Change-Id: I8cfaed6313c398deabdea809f53f65d4b7f4da42