Faster converter.

Faster tests to run, no need to set up
a full Drupal to run these tests.

- Quick reformatting

- _media_flickr_media_parse() and
_media_flickr_build_uri()
make sure what they return strings.

- _media_flickr_media_parse() and
_media_flickr_build_uri()
make sure what they return strings.

Improve readability.

Flickr introduced a short URL form. Default format for sharing photos
and albums.

 After Flickr include the users name and not the user id in the url
 is it probably more accurate to locate the user id by checking the
 photo or album/photoset.

Make the code clearer if we are passing user name or user id.

Save a image from Flickr to Drupal and verify that it is OK.
It uses Flickr external API and that bit should be replaced
by a local mock response.

Not used, empty and undocumented.

Flickr allow you to "star" your favorite images. This add
Support for these type of url. Example:
https://www.flickr.com/photos/eyespize/32739833993/in/faves-14718242@N04

Flickr renamed photosets to alubm. The url also changed. This add
Support for these type of url. Example:
https://www.flickr.com/photos/steinmb/3279274349/in/album-72157613786741477

Flickr have a function allowing users to explore images. This add
Support for these type of url. Example:
https://www.flickr.com/photos/paks/35329523855/in/explore-2017-06-15/

Provide correct link to media_flickr setting page.

 Flickr renamed photosets (sets) to albums
 https://www.flickr.com/help/forum/en-us/72157644091018883
 It also change the url from sets to albums though sets url still
 exists.

Issue #2075661 by brunodbo, steinmb, DamienMcKenna: fixed Change from using square_thumbnail to media_thumbnail

All of Flicker data sources are now https. Embedding content from non
https sources on a SSL enabled site will in most modern browsers be
blocked (mixed mode blocking).

Issue #2066485 by David_Rothstein. Download the original (largest) size photo from Flickr by default.