- replace double-quotes with single-quotes whenever appropriate
- fix indentation

remove exec() calls, replace /usr/local/ispconfig with variable, replace double-quoted strings with single-quoted whenever appropriate

Fixed a small bug in the nav.php which tries to lookup a custom module config file even if no module is selected and  enabled the dashboard module for the admin user by default after installation.

Added the configuration variable $conf['demo_mode'] in the config.inc.php file. It disables the newly introduced demo mode which limits certain actions in the interface part of ispconfig: the demo mode can be used to run the ispconfig interface part as online demo.

Changed quota setting for courier installations in authmysqlrc.master as ispconfig sets the quota with maildirmake command, so we do not have to specify a sql quota field.

Added document_root_www field to the web_domain table. This field contains the symlink path to the website.

- Fix some comments.

- The updater still asks for the port number, but with this update the default number that is shown is read from the vhost file as xaver suggested.

Implemented: FS#1252 - Add permission system based on user / password to app installer 

Fixed: FS#1229 - ISPConfig3 creates the desired e-mail domain twice (on master server AND on the selected Slave) 

Fixed error: ERROR 1101 (42000) at line 390: BLOB/TEXT column 'destination' can't have a default value

- Added a fix for opensuse regarding issue: FS#1250 - smtp file in pam.d directory on some distributions is world readable.