[feladat @ 271]
Password of Poweradmin administrator is now asked (and used) during installation procedure, avoiding the need of using a default password.
[feladat @ 270]
Added validation for SRV records. Closes #45. Updated validation for TXT records to allow for DKIM. Closes #49. Renamed is_valid_mx_or_ns_target function to more generic name is_valid_non_alias_target.