Merge pull request #119 from VanessaE/master

Give crossing proper textures
Escape microcontroller code in formspec
Upgrade CC-BY-SA License to 3.0

Permitted according to section 4b of CC-BY-SA-2.0:
"a later version of this License with the same License Elements as this License"
Add LICENSE.txt

LGPLv3 for code,
CC-BY-SA-3.0 for everything else
This should makes it easier for packagers of distributions
Update Microcontroller Tutorial and add .odt source for the .pdf
Make blinkyplants toggleable
Merge pull request #124 from qwrwed/master

Make blinkyplants toggleable
use 'wood' group for crafting pistons, pressure plates, and noteblocks