Basic interpreter for the DS

Changelog:
- new dashboard with save, run and load icons (touch to enable)
- cursor is off the screen for save and load
- key combination to break: you can now hold ‘A’ and ‘Start’ at the same time to break a running program (eg if you get stuck
in an infinite loop)
- all keys are now supported for key() operator, including L and R keys and Start and Select keys Summary of values returned by key():

X: 200
Y: 201
A: 202
B: 203
Left: 204
Right: 205
Up: 206
Down: 207
L: 208
R: 209
Start: 210
Select: 211

- input statement bugs fixed