Obstacle avoidance: Get out of obstacle routine

[SyrianSpock]

When set properly, our obstacle avoidance works wonders. The main bottleneck now is encountered when our robot think it's inside an obstacle (usually opponent or ally) and stops moving. We need a routine that safely get us out of the way and then leave the path planning take over again.

Idea: turn inplace until facing the measured center of the obstacle, then move in radially opposite direction.

Relates to #186

[antoinealb]

For reference, here is how Microb used to do it: https://gist.github.com/antoinealb/b56db064694ef4f0ccce00827664b4cb

Search for escape_from_poly.