This reverts commit c22330fd.

This enables access to all UserSessionService objects from within the
application. This could be used to send events to all session users.

This patch uses an in memory storage of logged in users. Every time
users send a (online) heartbeat the last known active timestamp of all
users will be checked and inactive users will be removed from active
user list.

This should perform much better.

Socket.IO about changed active user count.

prevent duplicates if the client uses Socket.IO and still sends the
**/online ping.

server.

server.

UserService.
Added a scheduled method to delete inactive users from
user2sessionLegacy Map.

implementation updates.

interfere with the existing HTTP polling solution.

Some features still need to be ported:
- update session attribute lastOwnerActivity in CouchDB
- add session to visitedSessions in CouchDB
- check if session is locked

This patch should increase findbugs report and solve some issues that
will occure:

* Doing operation on NULL object
* Using wrong object type in hope of magic object casting ;-)

* rename methods to clearify that this are sockets

CouchDBDao:
 * Removed obsolete method currentTimestamp()
 * Explicit IOException catch that indicates communication error

UserService:
 * Log if store file could not be created

All relevant information about users (e.g. session mebership) are
accessible via UserService.
The method IUserService::getCurrentUser provides information about
the actual logged in user. If no user is logged in, this method will
throw a UnauthorizedException which will end up in 401 HTTP error.

* Make guest login working with new UserService
* Reuse existing guest username
* Adapted tests

switch to oauth2 authentication which allows facebook, twitter, google
etc authentication