DataAssociator* became part of Fixture in unit tests for DataAssociator.
EstimationFilter's gained initialize(vector_t,vector_t) method,

which is not pure virtual, but is overloadable, to allow filters
initialize their internal state based on given conditions (like initial
measurement with given certainty).
KalmanFilter overloades this method.
Track and TrackManager use EstimationFilter new interface's facitlity (initialize(vector_t,vector_t) method).

To properly setup filter when initializing new tracks.
Now there is a distinction between first (initial) state of Track and
it's further states, based on incoming measurements.