Handling For: Warning: Invalid argument supplied for foreach() on lines 54, 141 and 178. - Empty Arg Array.

Updated english languages files
Updated czech languages files

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

- fix indentation
- get it nearer than similar server/lib/ files

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.

Patch from Filip that enables settting of sys_user.modules and sys_user.startmodule via client_add remote API call

Fixed: FS#1220 - /var/vmail/(domain)/(user) directories and files not delete when mail_user is deleted via remote.