Upgrade Jetty to version 11.0.11 using Java 11

Current Situation

• Branch 2.4. of JS7 makes use of Jetty 9.4.x that reaches its end of life.

Desired Behavior

• JOC Cockpit ships with a current 11.0.11 release of Jetty.
• Users of JS7 have to use Java 11 as a minimum version.
  • This change does not affect use of Java 1.8 with Controller and Agents.