[meta] photos 6.0.x plan

The module is ready for some pretty major rewrites including using the entity api for album images. Please post any other feature requests and link them to this issue.

Currently these features are in the works:

Images:
Create new entity for image and move title, description etc. to fields. This will also enable the field system for adding additional fields to images. This should also take care of translations and revisions (if needed).
#3101120: Convert album images to use the Entity API

File system support:
Add support for s3 bucket and other external file systems if needed?

Additional features:

Albums:
Deeper views integration for albums. More default options to choose from.

Blocks:
Grid pager. Maybe some fancy ajax browsing.

Slideshows:
Integrate flexslider as an option for album cover.

Editor:
Add button to ckeditor (or media option?) to embed album and options for cover / images / slideshow / colorbox gallery (linked cover or album title).

Settings:
Cleanup some of the settings and options.

Documentation:
Update D8 documentation.