General tidy up and plough through TODO list.

General tidy up and plough through TODO list.

Rewrote intro at top of file to reflect my better understanding of how it
the memory mapping works.

Clear the DONE list and move some thoughts into the TODO list.

Remove RECERR from RAY_DEBUG

Start to use a desired network parameter structure, only used in download
code as I've realised that there are some problems with the idea.

Break up ray_rx, and move the data packet handler into a seperate function. This meant some knock on changes in ray_rx_mgt/ray_rx_ctl to do with
mbuf freeing.

Remove some debug code/XXX comments that are out of date.