Report exceptions via ImageJ 1.x's very own mechanism

Signed-off-by: Johannes Schindelin <johannes.schindelin@gmx.de>
Allow overriding the hard-coded path to the .lsm file

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

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