This reverts commit df9835efafd13685251749bc210c0b96a18a96a5, reversing
changes made to ec45af8bfa9222a807c075dd1db4b5aa798bba03.
Conflicts:
hardware/arduino/variants/mega/pins_arduino.h
libraries/Ethernet/examples/PachubeClientString/PachubeClientString.ino
- moving back to multple cores per platform
- using target instead of platform
- moving per-board and per-programmer preferences out of Preferences.java and into a new Target class
- adding a new "target" preference
- support for platform:value values in board preferences for bootloader path and core
- XXX: need to support platform:value syntax for board upload.using preferences.