Smartqueue_taxo may alter subqueues it doesn't own

Problem: Smartqueue_taxonomy could accidentally update or delete the wrong subqueues when terms are updated or deleted. This might happen because the current SQL just searches for subqueues with a reference that equals the term ID. However, regular nodequeue subqueues store the queue id as the subqueue reference (and other smartqueue modules could store any arbitrary data as the reference). I marked this bug as critical due to the potential for data loss.

Solution: Make sure only smartqueue_taxonomy subqueues are deleted. Add WHERE owner = 'smartqueue_taxonomy' to queries.