Fix issue when DNS zone import fails silently with OK message if $TTL is missing from the input file because TTL can not be null when saving SOA to database.
Solution: if TTL is null then simply set it to 1 day - 86400 seconds (as per RFC 1912 recommendations).
I encountered few services that export a dns zone without global ttl set (ex: GoDaddy).

Fixed issue #3955 DNS module: Limit for maximum zones can be circumvented with "import zone file" function.
Removed TODO string in error template.

- changed/harmonized order of clients in client select fields ("ORDER BY client.company_name, client.contact_name, sys_group.name")

Fixed/Implemented: replaced intval() by $app->functions->intval() in all interface functions due to big number problem in intval()

+ Added DNS-import, not finished. Needs language-variables and better way to parse SOA-record and possibly some cleaning.