Upgraded clock distribution on radio hub boards

[tmolteno]

Use a zero-delay clock buffer in place of the jitter cleaner, driving a RC low pass filter.

• Tune filter to achieve the right output level, and reasonable cut-off. (4th order Butterworth) http://www.changpuak.ch/electronics/butterworth_lowpass.php
• Shift board to KiCad
• Reuse existing radio modules.
• Use new driver chips.