Turtle sliderule

Turtle sliderule for Turtle Blocks on Sugar (or Gnome)
Use A and D to move upper scale

Challenges:
Complete the rectangle representing each slider
Create more markings at useful intervals
Create alternate scales, CI, A, K, S, T, LL, Ln
Add a cursor
Mouse input
Circular sliderule
Replicate all the features at http://wiki.sugarlabs.org/go/Activities/Sliderule

(note there is a redundant multiply by 1 operation to circumvent a Turtleart bug, V96, fixed in V99)