Optiboot Verison 8.0

Now with do_spm() feature (allows applications to write to flash memory by calling code in optiboot.)
This should mean that this repository is now up-to-date with respect to features and platforms added in the MCUDude mini/mega/mighty, and the SpenceKonde Attiny cores.

Interim 7.0 release...

7.0-180815

Help Text for tinyxx7

Optiboot v6.2

Mostly, this is for testing the Arduino IDE 1.6.4 Board Manager mechanisms.
Not a production release.