doc: Improve overall documentation and fix minor issues

Fixes:
* Turn url into a clickable link in Markdown using <http://>
  (unlike wikitext, Markdown doesn't autolink urls).
* Override method name as indexed for oo.getHash.keySortReplacer.
  (defaulted to being indexed as oo#keySortReplacer since it uses
  last property level + class name, which works great with
  Foo.prototype or jQuery.fn, but less so in this case).
* Link plain text identifiers that weren't being recognised
  (oo.getHash -> OO.getHash etc.)
* Remove useless descriptions so they show up when querying
  items that need descriptions.
* Remove erroneous @example.
* Fix ignored "bindings" @property in EventEmitter.
  It wasn't being picked up because @property is not supported
  inside an @constructor comment.

Consistently:
* Omit redundant @method.
* Use @return instead of @returns.
* Start captions with a capital.
* Treat primary item (event, method, class, property) descriptions
  as sentences ending in full setop.
* Treat secondary item (param, return, etc.) descriptions
  as captions not ending in a full stop unless they form one
  or more paragraphs.
* Primary item descriptions should start with a single line
  in the imperative mood: "Get this", "do that", "make something";
  as opposed to: "Gets this", "Does that", "Makes something".
* Indent continued line with one extra space.

Change-Id: I25346437c95b1440341f4c1399afb93a6dd3ded1