Added 'mighty_twox-2560' target to SConstruct/SConscript
Added override for 2560 to use stk500v2 protocol for 2560 in SConscript
Added 'mighty_twox-2560' target to supporting sh scripts.
Merge pull request #93 from jake-b/master

Added "mighty_twox-2560" for Rep2X's with Atmega2560's