Grunt: Clean up

* Use jshintrc:true which lets grunt defer autodiscovery of the file
  to jshint instead of forcing it to '.jshintrc'. This allows us to
  override certain settings from a subdirectory, to match behaviour
  of standalone jshint.

* Sort modules.

* Use plain string instead of single-value array.

Change-Id: Ib5cd48f3ff0367b8fc84627c29e4fb32452087c0