Media: enhancements

[Davide Favia]

Lot of enhancements for "Media".

Model:

• Starred.
• Resource URI.
• Resource URI with full host.
• Metadata (exif if isImage = true).

UI:

• Pagination.
• Starred.
• Author.
• Contextual uploads.
• Search media inside popup (e.g covers, media list).
• Import from external media providers (Youtube, Vimeo, Twitter, etc...).