Improve metadata storage (#37)

* Updated config path to specify metadata storage path

* Removed metadata column from DB, replacing it with filepath columns

* Updated app to store compressed metadata; automatically download thumbnails

* Ensured metadata is deleted when other files are deleted

* Updated docs

* Added inets to application start so http calls work in prod

.iex.exs

@@ -13,6 +13,7 @@ alias Pinchflat.Profiles
 alias Pinchflat.Sources
 
 alias Pinchflat.MediaClient.{SourceDetails, VideoDownloader}
+alias Pinchflat.Metadata.{Zipper, ThumbnailFetcher}
 
 defmodule IexHelpers do
   def playlist_url do