Do not override -Dplugins.dir=... from ImageJ.cfg
Do not override -Dplugins.dir=... from ImageJ.cfg

Jerome Mutterer pointed out that -Dplugins.dir=... settings in
ImageJ.cfg are always overridden by the ImageJ launcher.

Fix that.

Signed-off-by: Johannes Schindelin <53fb8db7833fca1e1746dd8592f61048d350f64c@gmx.de>

imagej/imagej-launcher,imagej/imagej-launcher,imagej/imagej-launcher