This reverts merge request !1033

This reverts commit c97bed44.

Added a server migration mode setting which will be used to prevent that LE tries to recreate certs during a server migration.

FS#3526 - Add option to disable BIND zone check (the intention for the feature request was more to hide log-messages and not to disable the named-checkzone-call)

- http://en.wikipedia.org/wiki/SPDY

-Added a new option "Network Filesystem" under System > Server config > Web to toggle on / off the _netdev option for the bind mounts in /etc/fstab

Removed backup_dir_mount_cmd option from Sysstem > server config. The option has been replaced by a script /usr/local/ispconfig/server/scripts/backup_dir_mount.sh. If this script exists, is exacutable and is owned by the root user, then it will be executed upfront of the backup jobs when the option "Backup directory is a mount?" is enabled in server config settings.

- Updated Linux Distribution detection to recognize all wheezy sub versions correctly.

--------------------------------------------------------------
Feature can be activated over admin mailserver settings. when activated websites uid is used instead of standard vmail-uid. this only takes effect if web and mailserver are on the same server, otherwise it will be old behaviour. switching this setting when mailboxes exist doesn't matter. Mailboxfolder will be created with website uid for this. access of postfix and dovecot now works over mysql-table mail_user. virtual_uid_maps is changed from static to mysql-table. for dovecot<->postfix communication protocoll is changed vrom lda to lmtp. disablelmtp-column is added to mail_user-table. uid and gid can be overwritten by remoting.
ONE OPEN ISSUE: since remoting has completly changed and mail_user_add function is missing at the moment, this function now was inclulded again. it is important to add the both new lines to the future function and then remove this new one.

- Added options to use a mounted backup directory. This allows for remote backups, e.g. vis sshfs to a backup server. The backup script checks if the backup directory is mounted, and if not, tries to mount it.