Addon catalogs + manifest.behaviorHints

[Ivshti]

Implements an ability for addons to provide catalogs with addons, therefore adding the addon repository feature to Stremio

See #28

This option seems least cumbersome to implement: "alternatively, addon catalogs will be hidden behind a required property, and we will instantiate CatalogFiltered with some extra prop already passed;"

Others have problems: .addon_catalogs requires another generic trait, makes things much more complicated, for essentially what is the same data structure as .catalogs; as for resource_name, it's weird cause .catalogs implies a catalog resource

Checklist:

• items_group should use CatalogError
• consider using items_group for CatalogFiltered or alternatively use try_from directly, to make it polymorphic
• preview Descriptor or generic Descriptor
• implement CatalogAdapter and manifest.addon_catalogs