Add client logic and admin pages to support SP

Add client logic and admin pages to support SP

In the node configuration it's now possible to specify optional
Service-Proxy username and password, if none is specified the ipauthentication
will be used instead.

Also, Provided are DB shema migration hooks and the module is versioned
(as those two seem to go together somewhow). To update the module's DB table
one need to run the update.php from the root of the Drupla vhost.