[gta02-core] unit style changes and ECN0017 (BT to main PCB) -> Done

[Werner Almesberger]

BT is good, too. Having me as author and reviewer on ECN0017 may look
a little incestous, but there's an invisible commit by Dave between
the two that makes it alright.

Then I changed a number of inconsistent units:

- capitalization (100N -> 100n, etc.) mainly in wlan.sch, but also a
  few in modem.sch and one one in pmu.sch
- SI prefix replaces decimal point: bt.sch

- Werner