Backport the DNS code from 1.3-dev for speed and usability reason

Description

backport the dns code from 1.3-dev for speed and usability reason (see #5670 (closed)). The code is too slow to be really be usable in a real case scenario

Source FusionDirectory Version

1.3-dev

Destination FusionDirectory Version

1.2-fixes

Plugin with the new code

Dns

Reason of Backporting code

speed reason, too slow to be used in real world case, render plugin barely usable in zone editing and removal

What defect does it correct

Speed up deletion and saving by only touching record needed to be affected in place of the whole

Additional Information

Critical on certain customers site, OpenSides, Inalco