Optimize Micronet device rules to only apply to connected devices

[craigpratt]

Currently each AP gets configured with the Micronet rules for all Services/devices in the AP group.

NetReach could reduce the number of SDN rules (and table sizes) by only writing rules for known-connected devices - esp now that the NetReach agent maintains a more robust list of connected devices.

To retain the currently level of robustness (that allows devices to connect even if/when the AP loses its connection to the NetReach controller) the AP will need to retain a cache of the AP group service- and device-level metadata. But this is something that should be performed anyway to allow for more granular GET requests to retrieve just those Service/Device objects from the Controller that are signaled "changed" via MQTT.