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.

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.

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- Installer adds Apache and nginx user to ispapps group.
- Installer makes sure that /var/www/apps has 755 permissions.

- Added support for new default named.conf views layout.

• Added configure_dovecot function
• Updated functions configure_postfix, configure_pureftpd, configure_apache, install_ispconfig, configure_apps_vhost
• Bug fix in configure_amavis where installer was not including the ispconfig config file
• Bug fix in configure_apache where in suphp.conf the php handler line would be duplicated through updates
• replace double-quoted strings with single-quoted whenever appropriate
• changed inline comments to coding standards
• fixed OS specific paths
• changes to installer_base 1) add_database_server_record added os specific override of awstats paths 2) find_installed_apps courier not detecting correctly for gentoo

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

Implemented: FS#973 - Gentoo support for installer. Fixed FS#974 - Directory mode for firewall configuration