More of these double to floats cast problems.

Signed-off-by: Jean-Yves Tinevez <jean-yves.tinevez@pasteur.fr>
TGMMImporter: extract a rough spot radius.

Tried to derive it from the precision matrix, but obviously it does not
work well. I am not sure I understand well how I should do.
Signed-off-by: Jean-Yves Tinevez <jean-yves.tinevez@pasteur.fr>
More float vs double problems.

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