Fix bug in context command.

Optional arguments have been moved to options.
Because options must be given before arguments (blame karaf) the command to create a context for a opwnflowswitch has changed:

protocols:context -p protocol.floodlight.switchid="00:00:00:00:00:00:00:03" openflowswitch:s3 floodlight noauth http://<controller_ip:port>

The command now checks there are additional parameters in the context before trying to access them (avoid NullPointerException).
Merge pull request #675 from isartcanyameres/fix/context-command

Fix/context command