- write sieve filter to sieve subdirectory into ispconfig.sieve
- link .sieve to sieve/ispconfig.sieve

This script deletes zones on PowerDNS Slave servers, when
the master does not have a SOA record for it (delete zone on master).

configure_amavis() adds some extra lines to postfix's main.cf & master.cf
which are not required and are leading to malfunction when amavis is not installed.

 - refresh, retry, expire and minimum were missing in the SOA record which was/is OK
  because pdns has defaults for this, but this gives the user
  the full options which are configurable from the UI

+ drop/replaced pdns service reloads
 - the initscripts reload function was called which internally does 'pdns_control cycle',
  which is a quick service restart. This is no needed in pdns to
  load the new zone data. All updates are available without service reloads.
 - to be sure the zone data is really loaded 'pdns_control rediscover' is called
 - for pdns versions starting from 3 (DNSSEC) all zones must be rectified, implemented this using pdnssec.

+ send notify to slaves
 - implemented using pdns_control,
  this enables zone transfers to slaves (maybe this never worked before, because auf the service reloads)
  hint: use supermasters table on slave server for zone autodeployment, but you need an extra cleanup script
  for deleted zones for now

+ fetch Slave zone from master
 - call 'pdns_control retrieve <zone>' for new slave zones

+ added fix from FS#3121

+ code cleanup

add amavis-configfile-location for centos 6.4; add amavis-initscrip-name for centos 6.4; fixed missing private_key in mail/mail_domain_dkim_create.php