jshint: add .jshintrc / .jshintignore files

jshint: add .jshintrc / .jshintignore files

* More commits to follow that further fine-tune the settings and fix
  lint errors in the actual files.

* Quick how-to on how to use jshint from the command-line interface:
 - Prerequisites: node and npm
   http://nodejs.org/
   http://npmjs.org/

 - `$ npm install -g jshint`
   https://github.com/jshint/node-jshint/

 - Done!
   All: `/mediawiki/core$ jshint .`
   Dir: `/mediawiki/core$ jshint resources`
   Dir: `/mediawiki/core$ jshint resources/jquery`
   File(s): `/mediawiki/core$ jshint resources/startup.js resources/mediawiki/mediawiki.js`

Change-Id: Ia9297cb72c8faa7543ccfbdf48c7ee4e8af4ae17