Allow suppressing ImageJ 1.x' registering macros and scripts into menus

ImageJ2 brings a much improved scripting framework that offers most
notably consistency, where ImageJ 1.x' support for Javascript, Jython
and BeanShell is historically grown and lacks coherence.

Therefore, unfortunately, ImageJ2 has to disable completely ImageJ 1.x'
support for registering menu items for scripts and macros.

Signed-off-by: Johannes Schindelin <johannes.schindelin@gmx.de>
Let preinit() disable ImageJ 1.x' macros/scripts menu items

... to support ImageJ2 properly.

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

In certain circumstances, ImageJ 1.x' behavior to install Macro_Runner
menu entries for a limited set of scripting languages is less helpful
than intended: despite Fiji championing script support beyond the ImageJ
1.x macro language and doing a pretty good job at keeping it consistent
between the languages, ImageJ 1.x' script support is very heterogenous.

Even worse: ImageJ 1.x' script support insists on putting the downloaded
.jar files into different places than Fiji (and this was completely
avoidable). ImageJ 1.x insists on looking into those places, therefore
it will ask to download the scripting language support even if it is
present in the Fiji.app/ already.

Now with an even more consistent, elegant and extensible scripting
framework offered by SciJava common (with powerful features such as the
@Parameter style of interacting with the user), we have no choice but
to completely disable ImageJ 1.x' completely incompatible scripting
support.

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