[Media] Fix issues with database file storage

Fixed file quota as well.

There can be more than one file for the same filehash IF the url are different.

Possible states:
  - A file with no url and with filename is a local file.
  - A file with an url but no filename is a remote file that wasn't fetched,
    not even the thumbnail.
  - A file with an url and filename is a fetched remote file (maybe just a
    thumbnail of it).
  - A file with no filename nor url is a redirect.

Routes:
  Given these states, updated routes so that an attachment can only be
  retrieved by id and a file by filehash.

Major API changes:
  File::getByHash now returns a yield of files

Major UI changes:
  - Now remote non stored files are presented.
  - /view became preferred
  - Redirects to remote originals are preferred.

Many other minor bug fixes...

plugins/Embed/EmbedPlugin.php

@@ -189,14 +189,12 @@ class EmbedPlugin extends Plugin
             foreach (['xml', 'json'] as $format) {
                 $action->element(
                     'link',
-                    ['rel'   =>'alternate',
-                                  'type'  => "application/{$format}+oembed",
-                                  'href'  => common_local_url(
-                                      'oembed',
-                                      [],
-                                      ['format' => $format, 'url' => $url]
-                                  ),
-                                  'title' => 'oEmbed']
+                    [
+                        'rel'   =>'alternate',
+                        'type'  => "application/{$format}+oembed",
+                        'href'  => common_local_url('oembed', [], ['format' => $format, 'url' => $url]),
+                        'title' => 'oEmbed'
+                    ]
                 );
             }
         }