[DEV] PDAs now behave properly with unconnected power monitors

FIxes an issue where PDAs would throw a runtime and also a client error when a power monitor was not connected to the network when using the PowerON cart by identifying disconnected terminals and reporting them as such. Also cleans up a few typos in the template related to the power monitor and fixes a bug with the template missing a "value." in front of CellPct.