Add python scripts for Ryu controller that test OF-Config stuff

To make this work Ryu controller needs to be installed.
See scripts/ryu/of-config/README.md for details.

The scrips allow to obtain switch config through NETCONFG/get-config
and test setting a controller's role.

(Motivated by FlowForwarding/LINC-Switch#305).
Fix setting controller's role via OF-Config

(Motivated by FlowForwarding/LINC-Switch#305).
Fix dev target so that of_config is correctly started

(Motivated by FlowForwarding/LINC-Switch#305).