Make the Open Hardware Designs repo more accessible

[hamishwillee]

Pixhawk.org links into the FMU pages (e.g. FMUv2) for specifications and to the PX4 documentation for Pixhawk series, which is board rather than FMU centric (ie written for a different audience). This makes it very difficult for anyone to easily tell "up front" what each design delivers and how you can use it.

This PR

• [x] Add top level readme with info about designs, schematics, reference hardware, FMU versions, dev call, licensing, and trademarks
• [x] Each FMUvX folder gets its own README with outline of what is provided by design (schematics, pcbs, pinout docs, bom - whatever is actually in folder), the reader software needed, and links back to the parent for all the detail.

The theory is that the entry points clearly point to where more detail can be found about licensing etc.

I would also like to:

• [ ] Confirm gitter for the discussion channel - and if so, move it to Pixhawk/hardware.
• [ ] Add gitter to pixhawk.org site, and remove the discussion board links.
• [ ] Add link to dev call info to the pixhawk.org site, once this is merged.

[hamishwillee]

Thanks @bkueng. Appreciate you already reviewed this and deferred to Lorenz, but I added a few specific questions you might be able to help with. This also got split a bit more to highlight that the project delivers designs for more than just FMUs. A little more "bitsy" but more modular.

1. Do you think it is worth adding a FAQ to at least answer:
   • What is "a Pixhawk" - basically explain that a pixhawk is brand and product name. It is not "any product or design based on Pixhawk project FMU standard".

[bkueng]

What is "a Pixhawk" - basically explain that a pixhawk is brand and product name. It is not "any product or design based on Pixhawk project FMU standard".

That would be useful. I see this more as something for pixhawk.org, no?

[hamishwillee]

What is "a Pixhawk" - basically explain that a pixhawk is brand and product name. It is not "any product or design based on Pixhawk project FMU standard".

That would be useful. I see this more as something for pixhawk.org, no?

A website is really a marketing exercise, so not the best place to explain what you're "not". This might not quite be the right place either, but I'll see how it can be fitted in.

We could possibly have a proper gitbook library in the same way as our other ones. This could potentially pull out much of the px4 autopilot hardware information that we would link rather than reproduce. Haven't had any comment on the idea from @LorenzMeier.