Fill out erase and read flash functions.
Allow write_command to take an address.

Defaults to 0 and also use default addr=0 to clean-up APSEthernetPacket constructor.
Add APS2:: namespace to new write/read commands.
Cleanup some "unused variable" warnings.

Makes it easier to see what's actually wrong.
WIP: almost there - compiling now
Building cleanly but not tested....