Add $watchCollection(obj, listener) API to angular.d.ts

https://github.com/angular/angular.js/blob/master/src/ng/rootScope.js#L362

Signed-off-by: Gregory Petrosyan <gregory.petrosyan@gmail.com>
Merge pull request #1059 from sporttech/angularjs-watchcollection

Add $watchCollection(obj, listener) API to angular.d.ts