Implement direction() -> (0-360) function.

[yohell]

Calibrate compass:

• Goal: make function direction() that returns the direction of the robot relative to the arena:
  ** Unit: degrees (0-360)
  ** counterclockwise (like in maths).
  ** 0 is parallel with X axis direction along long wall toward windows .
  ** 90 is parallel with Y axis direction along short wall toward main big room
• Method:
  ** Spin, plot compass values.
  ** Enter mean range (minmax) values into code.
  ** Find directions of the walls:
  *** Tell robot to drive straight in compass direction X. Adjust X until parallel to long wall.
  *** Make sure Y is right angles to X.
  *** Enter direction of walls into code.