PAM authentication feature + several bugfix

[PDS-GH]

• Fixed cannot input domain in 'DNS search domain' field
• Fixed cannot input multiple entries separated with commas
• Fixed log entries missing for date from 1 to 9
• Restricted 'Common Name' field in certificate tab to alphanum
• Fixed iptables rule not added upon boot/reboot
• Refined iptables to remove previous rule before adding new rule
• Added 'PAM authentication' checkbox

[ghost]

Except for two things I found this pull request pretty decent. Good work!

[PDS-GH]

Thank you for the compliment. I just did the changes + commit + push.