Updated Artist avatars.
Merge pull request #224 from nanan9177/tutorial

Tutorial
Updated the turtle avatars to use the 180 angle version.
Merge pull request #225 from nanan9177/turtle_skin

Turtle skin
New blocklycore drop with x y info stripped out.
Remove unused scripts
Flatten strings json files
Merge pull request #227 from brandonbloom/no-loc-context

No loc context
Merged from Blockly master.