Introduce a focus area

The entity definition update for the 'crop' entity type in focal_point_update_8005() isn't working, it gives an error The "" entity type does not exist.

I've removed it from the update function. This means the Status report will show a Mismatched entity and/or field definitions error, that's a to-do to fix.

Also for some reason I needed to add a setName() call to the added focal_point_area base field in focal_point_entity_base_field_info_alter(), to avoid an Undefined array index "field_name" warning.

Ignore the above, all the entity definition update base field definition update needed was a call to the setTargetEntityTypeId method and I added a call to setProvider for good measure.

Updated patch and interdiff from #21 attached.

Added a check to ensure CSS width/height of the preview image is set, otherwise there'll be errors calculating relative coords of the focal area (divide by 0). Updated patch & interdiff attached.

Re-roll from 2.x-dev.

Adding focal_point_area.js back to patch. In focal_point_area.js, replaced reference to jQuery once() with Drupal once().

Moving this to the 2.x branch, which is where new features are being added.

Wouldn't you just use https://www.drupal.org/project/image_widget_crop → then perhaps?

If yes, we could close this won't fix and link the module as alternative on the module page?