Abstract bulk/quick input operations

* Abstract bulk/quick input operations
* Add API filter `cbqe_validate_default`
* Add trim validator to settings
* Auto-suggest for tag-based taxonomy during bulk and quick editing
* Prevent extraneous options from showing in edit screen columns
* Refactor bulk/quick custom box operations
* Remove auto-suggest and force reset options - now part of bulk operations by default
* Sample configurations provided on initial save
* Show unset category/taxonomy checkbox in bulk edit
* Test checkbox, radio, and select with 0/1 options
* Unset checkbox values
* Unset radio values
* Unset select values
* Update TODO
* Use WordPress's own taxonomy handlers for category and tag inputs