squash! Show the full version even in the LegacyUI

As a consequence, we have to access the static version directly in the
IJ1Helper to avoid an infinite recursion between IJ.getVersion() and
legacyService.getLegacyVersion().
Force the initial LegacyUI status bar to show the correct version

The "correct version" being, of course, the full ImageJ2 version
including the legacy version.

This is not possible otherwise because the legacy hooks can only
be replaced with a DefaultLegacyHooks instance once ImageJ 1.x is
fully initialized, which is unfortunately *after* ImageJ 1.x
wants to report its version.

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