Detail model

[Ivshti]

See this and follow the spec: https://github.com/Stremio/stremio/issues/655; some things of the spec are strictly view logic, but we should design the model and implement it here

it should have meta and libitem, other than all individual responses from addons;

furthermore, it should contain the streams within it; separate streams model is not necessarily a good idea, cause rendering streams depends on the meta (cause of video.streams and also the progress bar, libitem.state.timeOffset)

[nklhtv]

Done