[gta02-core] Layout - divide and conquer

[Werner Almesberger]

For the layout, we still have the issue that it's difficult to do
joint editing in KiCad, and "clean" merges can't be automated. One
way to overcome this limitation would be to split the layout into
sections that are only loosely connected, work on them separately,
and only merge the results.

I thing the following areas can be separared from a layout point of
view:

- GPS
- Main can (CPU, PMU, audio) and uncanned surroundings
- Telephony
- Top side

This still leaves a lot in a single lump, but it gives us the
possibility to break out one smaller yet significant subsystem to
get started, namely the GPS.

The drawback of starting with GPS is that it has all those
delicate RF issues. On the other hand, it may be good to get a
first rough draft and then give it a second pass at the end, when
we're more familiar with the process.

How does this sound ?

- Werner