Verify if the friend exists (#23)

Signed-off-by: Nico Rutishauser <nr@hotmail.ch>
Read / Write implemented (not tested yet)

Signed-off-by: Nico Rutishauser <nr@hotmail.ch>
Fixing the upload notification (NPE)

Signed-off-by: Nico Rutishauser <nr@hotmail.ch>