Fixed GUI typos, wrong links, added sync functionality, new screen for VirtualHosts

- Typo: Fixed typos (Virutal -> Virtual, etc) and some pages referencing 'setttings' instead of 'settings'
- Typo: Fixed typo within code : bowser -> browser
- Style: Re-indented code with only TABs in apache_virtualhost.xml
- Style: Force all IP address fields to use one of the existing interfaces.
- Sync: Modified the XMLRPC Sync configuration screen, based on Squid3's screen.
- Sync: Added actual XMLRPC synchronization code (auto/manual, based both on "carpsettings" and "hasync" structures,
  and confirmed successful replication (no luck yet with pushing a XMLRPC reload via pfsense.exec_php)
- VirtualHost: Added custom field to its own screen (still need to link it), for SSLRequire & Location specific stuff
- VirtualHost: Added custom Location settings to virtualhosts.conf generation (though it does not render properly,
  to prevent the XML field from being cleared when pushing "Save")
- Listening Options: New functionality to specify which ports Apache should be Listening on.