new settings page that allows plugins to integrate their own settings dialogs more with the existing ones

It's possible to use `OC_USER` as normal but the real stuff
is done by the `OC_USER::$_backend` class, setted using
`OC_USER::setBackend()` (this is done in inc/lib_user.php)

At start the choosen user manager is created
(e.g. OC_USER_DATABASE, OC_USER_LDAP)
and put into the global variable `$userManager`.

This is the variable to use instead of `OC_USER` class.

TODO: A better name than $userManager?

  * Support numeric types too
  * $WEBROOT variable was not necessary

This actually write all the key/value into the config.php.
The code in `writeAdminLisener()` is cleaner.
This is in prevision of new configuration options (e.g. plugin related)

PHP function names is case-insensitive so this change isn't
intrusive but improve readability of the code.

add Open Collaboration API support. You can now connect your ownCloud with the KDE Social Desktop and push notifications to your Social News Plasmoid. This requires KDE trunk or KDE SV 4.5