Fixed: FS#2378 - $conf['theme'] value in interface/lib/config.inc.php is overwritten (reset to 'default') on update

Implemented: FS#2283 - Add O option to dovecot transport in postfix master.cf so that X-Original-To: header is added.

Fixed (partly) FS#2310 - Template switch not working in mailuser module, for dashlets and the login page

- Added missing sys_tpl table to ispconfig3.sql and moved the definition of the table to the upd_0035.sql file as new tables cant be added in existing update files.
- added new ssl_key field to web_domain table.
- cleaned up unused code from apache plugin.

- install: touch auth.log
- login: write success/fail to auth.log
- cron: log rotation for auth.log

This option can be enabled under System > Server config and is named "Web folder protection".

- Added group (we call groups "circles" so that users don't mix them up with user groups) feature to client messaging section so that messages can be sent to either all clients/resellers or to groups of clients/resellers. TODO: add circle access control so that 1) a reseller can create circles that contain only his clients, not all clients, and 2) a reseller can send messages only to his own circles instead of all circles.

Merged revisions 3049-3051,3053-3054,3058,3070,3074-3077,3082,3086-3088,3091-3092,3094-3095 from stable branch.

- Make sure the apps vhost gets configured no matter if the ISPConfig interface is installed or not.

- Improved support for multiple PHP versions. Additional PHP versions have now their own form and database table.