Remove functionality from Acquisition Board source processor

[ChucklesOnGitHub]

Remove the DAC TTLs feature from the Rhythm Plugin which can now be achieved with more flexibility by a combination of other processors.
This option is not needed in the source processor.
Consider revising DAC High-pass filter too.

--Feedback from Acq Board Training sesssions--

[ChucklesOnGitHub]

The Noise Slicer has odd usage too, it would also need revision.
If it is going to be kept, it would be good to modify the interface so it looks related to Audio Out.