Adjust the pom.xml after the split-off from imglib.git

To make a stand-alone project, we need the developers, contributors,
issueManagement, mailingLists and scm sections, and the parent should
be pom-scijava, too...

This commit's parent corresponds to 8544c7aa(Move
non-imglib2-ij-specific manual test classes) in

	https://github.com/imglib/imglib

Signed-off-by: Johannes Schindelin <johannes.schindelin@gmx.de>
Work around not-yet-released class used in unit tests

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

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