Items to fix before next release

In the interest of pragmatism, here is a list of issues I want to ensure are fixed before we distribute a new native launcher to all ImageJ users:

[ ] The splash screen might not show up on Ubuntu 18.04. Testing needed.
[ ] Could not find X11 library, not running XInitThreads on Ubuntu 18.04. Track down why.
[ ] ignoring option PermSize=128m; support was removed in 8.0 No reason to keep this flag in the launcher anymore.
[ ] Using incremental CMS is deprecated and will likely be removed in a future release No reason to keep this flag in the launcher anymore.
[ ] Consider reverting #57 in favor of setting it on the Java side during startup.

CC @LauLauThom @stelfrich

imagej / imagej-launcher