Auto_Threshold - fixed minumum method

Added a break suggested by Antti Niemisto to make sure that the candidate for
the threshold is found after the first peak of the bimodal smoothed histogram.
Merge branch 'contrib' of fiji.sc:/srv/git/fiji into contrib
Bump Auto_Threshold to final 1.15

Signed-off-by: Johannes Schindelin <johannes.schindelin@gmx.de>