Refactor onResume method

I have revised the onResume method and removed unnecessary code. This
includes the delegation of protocol actions to the client controller as
well as adding an additional lock interface when a motion snapshot is
requested.

Signed-off-by: Konrad Reiche <konrad.reiche@gmail.com>
Add controller field to the main activity

Due to the fact, that the client controller is omnipresent in the main
activity for sending requests I have added a field for referencing the
client controller directly. This way it is not necessary to invoke
Client.getController() anymore.

Signed-off-by: Konrad Reiche <konrad.reiche@gmail.com>
Fix illegal state exception

I have found the reason why the application sometimes crashes after
trying to stop the detection. Apparently the controller state needs to
be redefined when onResume is executed. Although this bug was already
fixed with the previous commit the commit is used to document the bug
eventually. Besides that I have added Javadoc to the onResume method.

Signed-off-by: Konrad Reiche <konrad.reiche@gmail.com>