Option to process Geocode conversation using a queue.

DieterHolvoet → changed the visibility of the branch 8.x-4.x to hidden.

I started a new branch from 4.x and improved the implementation, both in the old 3.x and new 4.x branch:

• Simplified some naming and labels
• Moved the queue ID to a constant
• Stopped storing the whole entity object in the queue item data. Makes the row unnecessary big & makes it so the queue worker gets a possibly outdated version of the entity.
• Removed the drupal_register_shutdown_function. Instead, I added a check that only saves the entity if any values were changed, also preventing infinite loops but without needing hacky code.