Stream reading and writing of small and large files working, using write cache

Development snapshot; encryption stream wrapper now successfully writes files, and passes unit tests

Added unit tests
Fixed decryption of user private key at login
Added functionality to keymanager

applied some dependency injection to keymanager.php

provide ocs calls and keymanager functions to get/set both keys (private, public) of a user together

fixed bugs with keymanager integration
added unit tests

make use of the keymanager class in changekeypasscode()

fix calls in ocs.php