Use one top level source for all projects instead of one for each project

[johanpel]

Each example project has its own copy of the OPAE AFU top level, but it can be exactly the same top level for each project.

This was already reflected on this branch:
https://github.com/teratide/fletcher-opae/tree/multi_battery/hardware/opae

We need to rebase that on master so the removal of the JSON projects is retained, but the changes to have a single top-level remain, and then make a PR.