The ImageJ Launcher (a.k.a. the Fiji Launcher) program has been replaced with a
new launcher named Jaunch.

I made a concerted effort to preserve backward compatibility as much as
possible. As such, most features of the previous launcher still work in the
same manner.

However, the following features of the ImageJ Launcher are no longer supported:

* Launching in "Fiji1" mode (fiji.Main).

* Launching in "IJ1" mode without ImageJ2 support.
  A separate `imagej` launcher configuration now exists for this use case.
  But it does not use the ImageJ.cfg file; you must edit imagej.toml.

* Launching versions of ImageJ2 before 2.0.0-beta-8
  (released 2014-05-16) when the component+package structure was finalized.

* The undocumented `--tools-jar` nor `--only-tools-jar` options.

* Usage of Info.plist `<key>` elements to get and set launch configuration
  parameters on macOS. We need to keep the entire Fiji.app immutable in the
  future, to facilitate code signing for better distribution mechanisms.

* Best-effort automatic detection of headless mode on macOS and Linux.

* "Falling back to system Java" i.e. launching Java in a subprocess.
  Jaunch always uses libjvm functions.

See also https://github.com/apposed/jaunch/issues.
