Register controller with RFMonitor.

To register controller with RFMonitor, send a ControllerRegister message
to RFMonitor. The message has controller listening host, port and role.

Signed-off-by: Srijan Mishra <srijan23mishra@gmail.com>
Register controller when device comes up.

A controller was being registered with RFMonitor when ryu app was
initialized. Thus, it was not possible to keep a track on how many
devices a controller is connected to. Now the registration is done when
a device comes up. This helps in keeping exact count of devices to which
a controller is connected to.

Signed-off-by: Srijan Mishra <srijan23mishra@gmail.com>
Elect new master informed by RFMonitor.

RFMonitor informs rfproxy about the new master elected by ELECT_MASTER
message. The message is parsed at rfproxy and all the devices are
informed about the new master.

Signed-off-by: Srijan Mishra <srijan23mishra@gmail.com>