Read rows selected by $params and $include_additional from the field_config table. If $params include 'entity_type' or 'bundle' the field_config_instance table is joined on the 'id' = 'field_id' columns. Loads and installs the module(s) for the field(s) selected.
Mark instance $instance for deletion. In order for the instance to be marked, the module which defines the entity in the instance bundle must be active (enabled). If the entity defining module is inactive, deletion will silently fail. Actual deletion will be done during a field_purge_batch() operation started by cron.
