Update Podcasts

[archekb]

I have a few podcasts with 1000+ items and it's works very slow. I fixed it:

• add store;
• infinite scroll (for render many items);
• load episode;
• delete episode;
• reload episode if something went wrong while download;
• show downloading status (and auto-update it);
• add description cleaner (from html tags, allow only a few tags and add show it as html);
• fix width of track number column (for 4 digits numbers)

[archekb]

fixed for #103