Improved DNSSEC support

[Edmondas Girkantas]

Hi,

Today I pushed changes that improves DNSSEC support in Poweradmin, but keep
in mind that this code is experimental and it requires proper testing and polishing.
So do not use it in production.

What was added:
- Check box, which allows to select if zone should be secured or not ("add master zone" screen).
- Column with DNSSEC status for zones ("List zone" screen)
- Two buttons (Zone editing screen)
   - DNSSEC (here you can manage keys, display values of DS and DNSKEY)
   - Unsign this zone (disable DNSSEC support by removing keys)

Note: Poweradmin requires access to pdnssec utility.

How to enable DNSSEC in Poweradmin?
1. Get the latest code from git repo.
2. Add $pdnssec_use=true to your config file.
3. Add $pdnssec_command=/path/to/pdnssec (if it's not here /usr/bin/pdnssec)

Please use the Poweradming issue tracker on GitHub to report all bugs:
https://github.com/poweradmin/poweradmin/issues

--
Edmondas