Move to release-coupling with ImageJ2, ImgLib2

And while at it, get rid of the WEKA submodule (we can always check out
the correct version and modules/pom.xml will pick it up, but we no longer
make submodule commits reflecting the correct commit).

Signed-off-by: Johannes Schindelin <johannes.schindelin@gmx.de>
Stop handling uncoupled submodules

We want to refer to downstream projects by their release version
from now on. This is something we cannot easily do with profiles:
the former submodules' commit most likely points to the wrong version.

Signed-off-by: Johannes Schindelin <johannes.schindelin@gmx.de>
Build.sh: refactor the use of maven-helper.sh

Signed-off-by: Johannes Schindelin <johannes.schindelin@gmx.de>
Build.sh: no need to force-install the SSH uploader

Fiji's update site now operates on WebDAV anyway. Besides, the ImageJ2
updater's auto-installing of uploaders has stabilized now.

Signed-off-by: Johannes Schindelin <johannes.schindelin@gmx.de>
Build.sh: use the correct MiniMaven version

Signed-off-by: Johannes Schindelin <johannes.schindelin@gmx.de>
Ignacio wins the prize

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