Test ImuTracker  (#711)
Test ImuTracker  (#711)

Adds unit tests for ImuTracker to cover filtering of the gravity
vector and tracking angular velocity.
larics/cartographer,damonkohler/cartographer,larics/cartographer,cartographer-project/cartographer,cartographer-project/cartographer,wohe/cartographer,larics/cartographer,cartographer-project/cartographer,wohe/cartographer,damonkohler/cartographer,googlecartographer/cartographer,googlecartographer/cartographer,cartographer-project/cartographer,damonkohler/cartographer,googlecartographer/cartographer,wohe/cartographer,googlecartographer/cartographer,larics/cartographer,damonkohler/cartographer,wohe/cartographer