Debugging discrete-in

Coerce the currentState to always be numeric & use === tests
Catch the first spurious interrupt when x.value is undefined
Add more debug output
Add a second timer to get the first message out. This still fails at
node-RED startup when the node is not activeLow
Debug & tidy up

Make the colours the same as the RPi equivalents. Remove ‘BBB’ from the
node names.
Further debug output
Polishing discrete-in a bit

Commented out debug: added numeric validator
Starting to add scale factors & linearisation

Added breakpoints property to the node
Building the breakpoints editor (nearly there!)