More details in the catalog; new storage; no videos posters

[core1024]

Fixes https://github.com/Stremio/stremio/issues/578

Maybe fixes https://github.com/Stremio/stremio-local-addon/issues/26 too. The second issue is not very clear.

Here are some major changes:

• We collect the meta data along side the local files during the indexing;
• More meta data is shown in the catalog;
• The storage class is now more generic so we can reuse it for both metadata and local files;
• No more posters for videos as this causes huge downloads when open torrent with a log of series in it;
• The videos in series are properly sorted by season and episode;