Declare and use a library version string.

Signed-off-by: Jean-Yves Tinevez <jean-yves.tinevez@pasteur.fr>
Release v0.0.2

Velocity macro analysis:
------------------------
* The runs have to be longer than a certain threshold to be detected as
runs (as for pauses).
* The velocity threshold is estimated automatically. The user can still
change the estimate.
* The |Track mean intensity" in the exported table is based on the
detections TOTAL intensity.

Profile Viewer:
---------------
* A new TrackMate view, dedicated to image sequences made of single line
frames.

Signed-off-by: Jean-Yves Tinevez <jean-yves.tinevez@pasteur.fr>