Customized menu behavior.

Menu option "log-off" is not shown in
-LoginActivity
-RegisterActivity
Server: Stored connection details in properties file.

+ removed two tasks concerning the menu
Server: Deleted unused comment block.
Server: Correcting one logging-message for the registration process.
Re-activated encryption...

... as it is not possible to reconstruct the bug.
Therefore, a TODO for long-time observation has been added.
Synchronized en-/decryption as it is used in more threads.
Server: Implemented timeout-mechanism.

+ Added/deleted comments.
Deleted TODO-task.