implement reward valve as clock channel output

[nsteinme]

If desired output is a square pulse of duration d, then use a clock output channel, with duty cycle = 1, frequency = 1/d, run duration d. (If run duration is less precisely timed than the clock frequency then maybe use duty cycle=0.8 and frequency = 1/d*0.8 and run duration = d/0.8?)

The point is to free up an analog output channel, and make it so the reward does not interfere with analog outputs.

The change needs to happen in hw.daqController, by adding an option to use special output commands when the channel is a clock output type.

[k1o0]

I believe Jai implemented this. @jaib1 do you have a link to the code? What branches is this on and what were the changes again?

[k1o0]

@jkbhagatio Do you know where this code is? @pipcoen would like to use it for his experiments