Setup should remove older Jetty release if newer release is used

Current Situation
The Setup of the JOC Cockpit is already updated to install the latest Jetty Version 9.4.12.v20180830 due to security vulnerability.

When installing a JOC Cockpit over a previous installation old libraries of Jetty 9.3.x are not removed and results in duplicated libraries with different versions present in the file system. This behavior only occurs in 1.12.5. In the JOC 2.0-SNAPSHOT old Jetty libraries are removed correctly.

Desired Behavior
After installing JOC Cockpit over a previous installation no duplicated libraries should be present.

Workaround
Delete JOC_HOME/jetty folder manually before startig the installer

Maintainer Note
The Jetty Version 9.4.12.v20180830 has a new module for logging (console-capture) which is not compatible with the previous module logging.