Polyrhythm Clock FR: Add Run toggle input

[fractalgee]

I usually sync it from Clocked and would be good to have Clocked also turn on and off clock when it is turned on and off via it's Run output. A bit troublesome that the clock stays running even when external sync clock is turned off.

Great module otherwise! Thanks for these.

[jeremymuller]

The clock will turn off automatically after a certain timeout period from not receiving any more pulses.