plugins.svtplay: Make use of the validation API.
plugins.svtplay: Make use of the validation API.

Also removed support for RTMP streams as they no longer
seems to exist.

wlerin/streamlink,Feverqwe/livestreamer,charmander/livestreamer,programming086/livestreamer,Saturn/livestreamer,charmander/livestreamer,derrod/livestreamer,beardypig/streamlink,mmetak/streamlink,chrippa/livestreamer,Masaz-/livestreamer,gravyboat/streamlink,Dobatymo/livestreamer,Klaudit/livestreamer,chhe/streamlink,gtmanfred/livestreamer,streamlink/streamlink,lyhiving/livestreamer,Dobatymo/livestreamer,caorong/livestreamer,bastimeyer/streamlink,Klaudit/livestreamer,jtsymon/livestreamer,okaywit/livestreamer,derrod/livestreamer,gtmanfred/livestreamer,back-to/streamlink,back-to/streamlink,caorong/livestreamer,fishscene/streamlink,melmorabity/streamlink,lyhiving/livestreamer,chhe/livestreamer,wolftankk/livestreamer,flijloku/livestreamer,blxd/livestreamer,wolftankk/livestreamer,intact/livestreamer,blxd/livestreamer,sbstp/streamlink,chrippa/livestreamer,jtsymon/livestreamer,javiercantero/streamlink,programming086/livestreamer,ethanhlc/streamlink,okaywit/livestreamer,wlerin/streamlink,ethanhlc/streamlink,fishscene/streamlink,sbstp/streamlink,intact/livestreamer,hmit/livestreamer,javiercantero/streamlink,bastimeyer/streamlink,chhe/livestreamer,beardypig/streamlink,hmit/livestreamer,gravyboat/streamlink,Feverqwe/livestreamer,melmorabity/streamlink,chhe/streamlink,streamlink/streamlink,Masaz-/livestreamer,mmetak/streamlink,flijloku/livestreamer,Saturn/livestreamer