Add ability to set display intensity and neopixel intensity in RNS config

[tomuk5]

Please could we add the ability to set Rnode device parameters display intensity rnodeconf -D {0-255}
and neopixel intensity rnodeconf -np {0-255} via parameters in the RNSD config file under the specific radio interface.
Much in the same way as we specify radio frequency/spreading factor/coding rate/etc

for example by using displayintensity and neopixelintensity parameters:

[[RNode LoRa Interface]]
  type = RNodeInterface
  enabled = True
  port = /dev/ttyUSB0
  frequency = 867500000
  bandwidth = 125000
  txpower = 22
  spreadingfactor = 9
  codingrate = 5
  flow_control = False
  mode = full
  displayintensity = 1
  neopixelintensity = 255

This would save having to remember to configure the device via rnodeconf before use.