Use imglib2.version property for imglib2 deps

Previously, the imglib2.version property may have seemed gratuitous,
since ImageJ2 and ImgLib2 were being versioned together. But we realized
the folly of this approach, and the version numbers will soon be
diverging to give us more flexibility. So imglib2 dependencies must use
the correct property now.
Fix whitespace
Update Bio-Formats dependencies to 4.4.8

This change upgrades the parent pom-scijava to the latest version, which
now has bio-formats.groupId and bio-formats.version properties distinct
from those of SCIFIO. These Fiji plugins need to depend on Bio-Formats
4.4.8 (because the updater currently ships BF 4.4.8), so we use the
bio-formats.* properties instead of the scifio.* ones.
Use fiji.version property for inter-plugin deps

Previously, many Fiji plugins referenced each other using the
imagej.version property, which was not guaranteed to match the version
of the Fiji multimodule project itself (and in fact no longer does, with
the pom-scijava bump to 1.48, since imagej.version now points to the
2.0.0-beta-7 release instead).
Tell Maven that pom-scijava is outside the reactor

Otherwise, by default it will look in .. for the parent POM. And while
it typically will not find it there, it is better to be safe and ensure
it does not even try to look.
Upgrade TrakEM2 to the newest pom-scijava version

Signed-off-by: Johannes Schindelin <johannes.schindelin@gmx.de>
Use shorter URL in download-launchers

Signed-off-by: Johannes Schindelin <johannes.schindelin@gmx.de>
Merge branch 'dep-versions'

This upgrades to a new pom-scijava version.

Signed-off-by: Johannes Schindelin <johannes.schindelin@gmx.de>
Follow ImageJ2's SNAPSHOT versions for now

The development between Fiji and ImageJ2 is still very closely
related. For example, in the next weeks there will be a lot of work
reconciling ij-legacy with fiji-compat. For that reason, let's follow
ImageJ2's SNAPSHOT versions at least until ImageJ2's beta8.

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