More K1 artist move block changes

* Add a length parameter to simple move blocks
* Add a N/S/E/W letter to simple move blocks 
* Add simple jump blocks

_EDIT_:

![image](https://cloud.githubusercontent.com/assets/206973/2735388/61669060-c65f-11e3-8c78-22d56b041aa3.png)

Includes core change: https://github.com/code-dot-org/blockly-core/pull/66