Massive directory restructuring.

For the sake of my sanity, perhaps we should restructure the directories? Having a code/firmware/src hierarchy before actually getting to any code is annoying.

As git turns simple directory operations into massive logs, here's what I did:

* Delete code/proof-of-concept entirely

* Move code/util into util

* Move stl-views.gdb into the top level

* Move the contents of code/firmware into the top level.