Use ADC as input to DAC.
Fix small errors
Link DAC to ADC.
Change SYSCLK to 144MHz
Update to work with averaging
Update Ipython notebook
Merge branch 'dac-test' of github.com:kebno/beamformer into dac-test
Update for streaming to DAC
Make AUDIO PASSTHROUGH WORK!!!!!

Previously, I tried audio passthrough and it was terribly noisy.
Today, I discovered that at the sample rates I was using, I should
have had a MUCH lower analog input impedance.

I also figured that the buffers I was using were too small. Now
they are at much larger values (512) and things are better.

But another thing I added was the streaming averaging of the
ADC buffer (averge one half while other is sampled).

So, in the end I do not know exactly why things didn't work at
first, but they do now.
Merge branch 'dac-test'