Convert the DAQ monitor class into a standalone xDAQ application

Summary

Currently, the ShelfMonitor class creates an instance of the DaqMonitor class per back-end board, whether it is reachable or not. It is unpractical to use and doesn't scale with "missing" boards (this is the case at p5 where only odd slots are populated).

The idea of this issue is to convert the DaqMonitor into a xDAQ application, let's call it AMCMonitor that monitors a single board. It is the responsibility of the user to instantiate the correct number of applications. The AMCMonitor application does not provide a GUI, but export the monitored parameters through a JSON API.

In this organization, the ShelfMonitor only provides the web interface which aggregates the information from the available AMCMonitor instances.

This is somehow similar to the AMCManager and GEMSupervisor classes.

What is the expected correct behavior?

Each board is monitored by a single xDAQ application and the combined results displayed by the ShelfMonitor application.