Revision 460

- NLBConfig better error handling
- Implement payload so it attempts no processing of the image (I can now use it for ELF images!)
- Implement linux so it does what it has always done (but is now distinct from payload)
- Implement the new expr command so I can compute values (I got inspired)
- Micro fix to rom_fill_inbuf.c so we don't get back too many bytes (Thanks Ron)
- Fix for fallback_boot.c so it is always available.  Otherwise I can't say my boot succeeded.
- Added example config scripts for the p4dc6