Avoid querying for pdnssec ordering records at all
Add "WHERE" filters for TYPE IS NULL to record queries
Previous fix in Fix #194 only hides them from display, which
results in empty pages, incorrect pagination and random numbers
of records per page. PowerAdmin shouldn't need to see these at all
so filter them at SQL.
Merge pull request #212 from ktims/avoid-pdnssec-query

Avoid querying for pdnssec ordering records at all