Make LutFinder more robust

The luts/ directory need not exist at all. Deal with it.

Signed-off-by: Johannes Schindelin <johannes.schindelin@gmx.de>
Launcher: handle the executable name 'debug' earlier

It is quite useful to be able to get debug messages from the launcher
simply by renaming it to 'debug' before launching it. So let's activate
the debug mode really early, before even determining ij.dir.

Signed-off-by: Johannes Schindelin <johannes.schindelin@gmx.de>
Launcher: rename the 'debug' field to 'dry_run'

Because that is what it is...

Signed-off-by: Johannes Schindelin <johannes.schindelin@gmx.de>
Launcher: rename the 'verbose' variable to 'debug'

Because that is what it is...

Signed-off-by: Johannes Schindelin <johannes.schindelin@gmx.de>
Launcher: in debug mode, set the property 'ij.debug' to 'true'

When the launcher is renamed to 'debug' for verbose output, set a
tell-tale property so Java code can react to that.

Suggested by Curtis Rueden.

Signed-off-by: Johannes Schindelin <johannes.schindelin@gmx.de>
Launcher: in debug mode, crank up the log level

When the launcher is renamed to 'debug' for verbose output, set the
log level of SciJava's log component (which is used by ImageJ2 now)
to 'debug'.

Suggested by Curtis Rueden.

Signed-off-by: Johannes Schindelin <johannes.schindelin@gmx.de>
Launcher: do not write .desktop files in debug mode

... because the .desktop file would refer to the absolute path of
the debug executable, then.

Signed-off-by: Johannes Schindelin <johannes.schindelin@gmx.de>
Launcher (MacOSX): fix ext dirs detection

In the recent cleanup of the JRE discovery, the Fiji-specific ext dirs
(needed for Java3D on MacOSX) were lost.

Reported by Kris Sheets in http://fiji.sc/bugilla/show_bug.cgi?id=570

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