Bug 1014605 - [Browser][V2.0] Cannot add a RTSP shortcut on homescreen

* Add rtsp url support in the manifest.webapp of the bookmark app.
Merge pull request #24203 from begeeben/1014605_cannot_add_a_rtsp_shortcut

Bug 1014605 - [Browser][V2.0] Cannot add a RTSP shortcut on homescreen, r=crdlc