IJ1Patcher: avoid using transient class names twice

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

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

Signed-off-by: Johannes Schindelin <johannes.schindelin@gmx.de>
IJ1Patcher: Also fall back if imagej-legacy was not found

In case of version skew (e.g. because an update site does not depend on
ImageJ2 explicitly and therefore "forgets" to upload a corresponding
version to a new ij1-patcher), we really need to be careful to fall back
to strategies that are more likely to work.

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