Now with more firehose

We added realtime monitoring to the software. Now, if a value is read from a measurement device, you can get a push notification using HTTP long poll. This occurs without a significant delay, so this should make realtime applications possible. We intend to optimize this further in future releases by creating special schedules. In essence: you can subscribe to the firehose, or you can use the new sdm630_monitor command to subscribe to power readings.

In addition we tested the software with more devices, see the README file. We will probably rename the software in the next release because we now support all EASTRON smart meters available to us.