Migrate ryu-rfproxy to routeflow organisation

Signed-off-by: Joe Stringer <joe@wand.net.nz>
Change to the new Ryu event library

Ryu v2.0 changed from using gevent for event handling towards its own
ryu.lib.hub implementation, and introduces a dependency on the eventlet
library. This patch fixes rfproxy to work against newer such versions of
Ryu.

This is not backward-compatible with earlier versions of Ryu.

Signed-off-by: Joe Stringer <joestringernz@gmail.com>
Reduce scope of IPC

Signed-off-by: Joe Stringer <joestringernz@gmail.com>
Readme: Add FAQ section

Signed-off-by: Joe Stringer <joe@wand.net.nz>
Readme: Specify Ryu controller version dependency

Signed-off-by: Joe Stringer <joe@wand.net.nz>
Readme: Formatting fixes
Conform to pep8
Tidy up send_pkt_out()
Remove redundant code
Use ryu library for getting ethertype
Use new Ryu topology module to track datapaths