Bug 870711 - Fixes URL linking in SMS - r=julienw

* Rewrote LinkHelper to avoid a bunch of edge cases and overlapping links
* Modeled greatly after `android.text.util.Linkify`
* Co-Author credit for @lissyx for starting me out with an awesome unit test suite

Closes gh-10741
(cherry picked from commit a310b24b731d5a3c1779e65f112dc5ee88758ddc)