[BZ 1069662] (JON3-16) Adapt JON UI title bar to common Red Hat L&F

MenuBar rewriten using patternfly. Also added dropdown submenus to our main
menu (including hiding them when permissions are not met). Submenus more or
less copy our view structure - further discussion needed (if we even want
submenus, what content it has and how to show it).

Please do not merge this PR yet