mediawiki.js: Minor clean up of comments and code

* Put ternary on one line or separated over 3 lines.
* Whitepace inside parentheses (e.g. catch statement).
* Avoid trailing line comments.
* Capitalise description of parameters for consistency and to
  have it better stand apart from the variable name.
* Phrase primary method block description as a single line
  in the imperative mood.
* Avoid shortened urls inside documentation.
  (updated Modernizr ref to a release instead of git hash).
* Using store.enabled as boolean (null being falsey).
* Merge subsequent if-statements having the same logical purpose
  and body.

Change-Id: Ia1db9e54d528b2799187d80d2e3e22e31f74fb6b
Merge "mediawiki.js: Minor clean up of comments and code"