Simulator wip

Here's the GPS simulator!

- It flies in a circle!
- It has gaussian noise on its position and speed!
- It has configurable parameters!
- It can run forever, no numerical overflow!
- It is robust to large timesteps! 
- It does not have any measureable effect on CPU runtime!

- You can seamlessly switch between simulated and real data! All the normal operations run in the background!

- it has already helped me catch a bug in my Piksi driver
- Allows us to do hardware performance testing of peripherals!

- ITS AWESOME!
- MERGE IT!