Add Media Context and Media Bundle Condition plugins.

[steveoliver]

Adds 'media' context and 'media bundle' condition plugins for use with blocks.

[steveoliver]

While the tests introduced in this PR pass, the build is failing on unrelated Drupal\media_entity\Tests\Views\BulkFormTest.

[Berdir]

Note: ctools provides generic entity bundle conditions (using derivates). Unfortunately it doesnt provide context yet, but might be worth to consider relying on ctools for that.

Especially because adding your own will result in duplicate conditions for everyone who does have ctools enabled. That's currently already a problem with the node type condition but that's a problem that ctools has to solve.

[steveoliver]

Thanks @Berdir -- I'll look into ctools. I went this route since it seemed closest to Core.

[sylus]

Just wanted to say thanks for working on this, was definitely something I needed as well. I gave what was done currently a shot and works great.

[steveoliver]

You're welcome. Glad you found it useful. Indeed, Ctools provides the condition, but this is still helpful when you want the media context.

[steveoliver]

Rebased on latest in 8.x-1.x.