Issue #2839942 by pianomansam: Users with Publish all PDFs permission also need Administer PDFs permission

Issue #2828240 by pianomansam: BaseFieldDefinitions in FillPdfFormField are missing required "weight" display option

Issue #2713013 by FatherShawn, wizonesolutions, pianomansam: PHP message: Recoverable fatal error: Argument 1 passed to Drupal\Core\Entity\ContentEntityForm::__construct()

Also removed an unused public variable (we have a static function
somewhere doing the job).

Issue #2828227 by pianomansam: Default entity ID isn't required, but is assumed by FillPdfLinkManipulator

Fix fails along the way and create a config schema so that I can test
properly.

And some code style.

Now with real tokens again instead of the fake D7 token! We look at metdata
and stuff to figure out if it's an image field token! For great profit!

Snuck in a couple other fixes.

Turns out tokens don't get replaced with empty values anyway, so reversing
the replacement order was good enough!

And update the feature description.

So far, I have defined the interface. Need to actually implement the class
and move the logic from HandlePdfController.