Bump to just-released new parent version

This contains most notably the big switch to the legacy UI as default
user interface, at least for now.

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

Migrating to WelcomeService in SciJavaCommon
Add WELCOME.md

Adds the file that will be displayed when IJ2 is first run.