DIAL startup support

[Informatic]

Official webOS YouTube app can be started directly from smartphone YouTube app.

By default youtube is hardcoded as youtube.leanback.v4 (?) in DIAL server, but there also seems to be some support for dialAppName (?) property in app manifest.

Either renaming this app as youtube.leanback.v4, playing with dialAppName attribute, or patching the DIAL server altogether (at least for rooted devices) would be great.

[Informatic]

It seems like adding "dialAppName": "youtube" into appInfo.json is enough to get the app launchable via Android YouTube app. webOS app launches to login screen by default (not to a video that was requested to be casted) but this should be easily fixable)

(relevant path: /usr/palm/services/com.webos.service.dial/discovery-server.js)

[Informatic]

YouTube app gets launched with contentTarget param that is a https://www.youtube.com/tv?pairingCode=... URL.

Launch params are acessible as a JSON string in window.PalmSystem.launchParams (if not using webostvjs)

App relaunches via DIAL (connecting a mobile app to already running youtube tv app) need to be handled properly: https://webostv.developer.lge.com/develop/code-samples/app-lifecycle/