Coloc 2: fix small array index bug
Coloc 2: handle unavailable RoiManager gracefully
Coloc 2: fix typo
Coloc 2: Added Spearman Rank Correlation.

This adds an option to the Coloc_2 window, adds the Spearman rank correlation algorithm, some JUnit tests, and 2 test images.
Coloc 2: migrate to Imglib2
Coloc 2: use RandomAccessibleInterval instead of Img

The Img interface is nearly never needed within the plugin. Therefore
we can use a more abstract one.
Coloc 2: add override annotation and small style change
Coloc 2: add alternative Spearman Rank call
Coloc 2: fix Spearman Rank unit test
Coloc 2: fix Spearman T statistics calculation

The rho parameter should be used in the method, not the
class member.
Coloc 2: fix Spearman T statistics test case

The getTStatistics() method requests n, the number of data
points and not df (which is n - 2).
Coloc 2: fix Imglib2 related compilation issues
Coloc 2: get rid of some complier warnings
Coloc 2: adjust width of results tables automatically

The width of the tables is now the width of the available
space at maximum. However, it is extended as far as needed
for the content and as far as possible.
Coloc 2: reuse single array pixel look-ups during histogram creation
Coloc 2: don't scale histogram intensities up if maximum < bins

The 2D histogram's abscissa shows the intensity values of channel
one and the ordinate the one of channel two. If the maximum
intensity is higher than the available number of bins in X and Y,
respectively, the calculated coodinates get scaled down so that
the maximum intensities are on the last bin available.

Up to now this also happened when the maximum intensity is lower
than the number of bins. Of course, the coodinates need up-scaling
in such a case. However, simple upscaling brings in artifacts of
empty bins. To get around this, the plugin now doesn't do up-scaling
anymore. The resulting histogram fills therefore only a part of
the image space, but doesn't show artifacts anymore.
Coloc 2: do correct up/down rounding in histogram
Coloc 2: display information on mouse hovering an result histogram
Coloc 2: style changes
Coloc 2: refuse work on images with different bit depths