AVR8 soft core with support for SPI, pin shifting and custom core example

Jack,

finally - sorry it took so long - I am committing "Shifty" branch of AVR8 soft core for Papilio, with fully functional custom core example. You can see our conversations on GadgetFactory from about 1/2 year ago. I added specification document in the trunk, to explain the changes made, and also added some basic instructions on how code works in the case somebody is interested in using the custom core.

Thanks -Zvonimir