Special-case target directories for scifio and jai_imageio

The artifacts 'scifio' and 'jai_imagejio' exist in two incompatible
versions in the ImageJ ecosystem, unfortunately: Bio-Formats and SCIFIO
both have them. They do not interfere with each other on the class path,
though, so let's install Bio-Formats' versions into a different
directory until we can replace Bio-Formats with SCIFIO completely.

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