A new SetupThreshold() method is added to configure and control the
device signal notifications sent to the host. RSSI and error rate
based thresholds are initially assumed, but the interface allows
growing the method with additional threshold types.
Includes updates by Aleksander Morgado to improve documentation of the
new methods and properties.
Extended the ModemManager Signal interface to include 5G signal
information for RSRP, RSRQ and SINR via libqmi. Also extended mmci
to print 5G signal info.