K1 turtle: add dots every 50px
- Change dropdown images to include dots
Rename methods, remove redundant truth check
Remove now-redundant check
Refactoring based on code review
- rename drawDot_ to dotAt_
- extract method drawForward_ and move existing drawForward_ to drawForwardLine_
- remove some duplicate logic in joint code
- inline method startPathAtTurtle_ for clearer drawing logic
Remove unnecessary constant exports
Merge pull request #783 from code-dot-org/remove_unnecessary_exports

Remove a few unnecessary constant exports
Remove unused method
Draw joints using circles rather than dots
Merge pull request #782 from code-dot-org/joint_k1_artist_lines

K1 turtle: add dots every 50px