README: break AX211 documentation out

We now focus on the AX215.  So break the AX211 documentation out into
its own directory.
progs: Move 8051 programs to progs/ directory
README: Remove AX211 documentation

It's in the doc/ directory now.
fpga: Add FPGA control programs and firmware

This adds the firmware and contorl programs used to drive the
external hardware test jig.
fuzz: Break out 'fuzz' into its own file

It's getting unwieldy enough to warrant its own file.