Let --ij1 really start ImageJ 1.x, not Fiji1

Signed-off-by: Johannes Schindelin <johannes.schindelin@gmx.de>
Current Fiji is ImageJ2 + add-ons

Fiji no longer needs a special main class. Instead, it relies on
ImageJ2 to provide all the extension points into ImageJ 1.x -- insofar
needed -- and by default, fiji.Main hands off to net.imagej.Main anyway.

Signed-off-by: Johannes Schindelin <johannes.schindelin@gmx.de>
Merge branch 'fiji2'

Starting with the SNAPSHOT version of fiji-compat that switched Fiji
to hand off execution from fiji.Main to net.imagej.Main, Fiji is now
truly just an add-on to ImageJ. Therefore, there is no need to call
fiji.Main anymore (unless in outdated setups).

While at it, let --ij1 really call bare-bones ImageJ 1.x.

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