adding linky filter to ngSanitize

The linky filter is used to _sanitize_ (escape html) and linkify text

* added module for [ngSanitize filters](https://github.com/angular/angular.js/tree/v1.2.0/src/ngSanitize/filter)
* added [linky filter](http://code.angularjs.org/1.2.0/docs/api/ngSanitize.filter:linky) to angular 1.2 ng.sanitize module