Do not use ImageJ updater class outside Packager directly

Signed-off-by: Johannes Schindelin <johannes.schindelin@gmx.de>
Avoid depending on the updater Progress class for addDefaultFiles()

Signed-off-by: Johannes Schindelin <johannes.schindelin@gmx.de>
Update to the new updater

The new updater lives in a different package. To support the case where
installed packages do not *quite* fit the bill, we also sport a fall
back to the old package name.

Signed-off-by: Johannes Schindelin <johannes.schindelin@gmx.de>
Use the imagej.dir property

... but still fall back to ij.dir if imagej.dir is unset.

Signed-off-by: Johannes Schindelin <johannes.schindelin@gmx.de>
Avoid compile warning about unchecked cast

Signed-off-by: Johannes Schindelin <johannes.schindelin@gmx.de>
If ImageJ.sh exists, bundle it

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