Code style changes.

Signed-off-by: Jean-Yves Tinevez <jeanyves.tinevez@gmail.com>
Implements provider methods in detector factories.

Signed-off-by: Jean-Yves Tinevez <jeanyves.tinevez@gmail.com>
Add a public method to test settings validity for detectors.

Signed-off-by: Jean-Yves Tinevez <jeanyves.tinevez@gmail.com>
Use new detector factory design in TrackMate.

Could be simplified more. Since the factory has all the required behavior to be
used in the GUI, we can get rid of the provider at some places.
But first, let's focus on SciJava nagic.

Signed-off-by: Jean-Yves Tinevez <jeanyves.tinevez@gmail.com>