Fixed PHP Warning:  Undefined property wb of class app in /usr/local/ispconfig/interface/lib/app.inc.php on line 81

Start checks against local sites list for allowed reverse proxy forwards

First workflow for allow reverse proxy with different site names
for ispconfig panel.

TODO: Allow only for sites known to the system itself instead
of all or none.

- Use it like $app->conf('yourpluginname', 'config-key', 'value')
- omit the value to read the config value, provide it to set the value

Fixed login as

Fixed/Implemented: replaced intval() by $app->functions->intval() in all interface functions due to big number problem in intval()