Add mini-mission logic

[va3wam]

So far our code has implicitly had one goal or mini-mission. That goal is to stand still. We need too add logic to allow for different goals beyond standing still. These goals can include:

1. Move in a straight line forward a set distance
2. Move in a straight line backward a set distance
3. Spin on the spot (pirouette)
4. Move in a circle of various diameters
5. Move in a square of various sizes
6. Move in a triangle of various sizes