Added support for new karma file patterns:

Hi,

   The latest version of Karma supports a new files array format, one that lists objects with properties [ pattern | watched | served | included ].  

   files: [ {pattern: './**/*.json', watched: false, included: true}]

To get this working in my project I made a patch to grunt-karma to support these properties, and of course be backward compatible with simple pattern strings.

I also added support for task target options file list to merge with task global options file list.  I have my karma.options.files listing application common files for all tests, and then each target (unit/midway/e2e) can list their local options.file list, both lists will be merged.

   I updated the tests and the gruntfile to exemplify the various patterns in play.  

   Please take a look.  I hope you like.