Remove unused import

Signed-off-by: Johannes Schindelin <johannes.schindelin@gmx.de>
Do not override Edit>Options>Memory... any longer

Since imagej.git commit 021946ca6f(ImageJ Launcher: parse new-style
ImageJ.cfg), the launcher now prefers ImageJ.cfg over jvm.cfg. This
was done partially to allow ImageJ 1.x to use the ImageJ launcher
(rather than the previous, platform-specific launchers written in
Pascal and C++ or even using MacOSX' JavaWrapper.

So there is no longer a need to write out jvm.cfg in Fiji.

But since ImageJ 1.x refuses to write out a new ImageJ.cfg, we have to
write one ourselves if it does not yet exist.

Reported by Stoyan Pavlov.

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