Update jaxen-1.1.1 to jaxen-1.2.0 (dropping icu4j 2.6.1 that breaks Master plugins on startup)

Current Situation

• Use of newer Java releases e.g. after 1.8u251 (and similar for updates of newer Java branches) causes an incompatibility with the icu4j library (Unicode support) that ships with the JobScheduler Master and Agents (icu4j-2.6.1.jar).
• The Java update introduces incompatibilities that prevent the Master's plugins from working.
• The problem can be observed from the Master's log file (./logs/scheduler.log) like this:

  12 15:02:25.379 c.s.j.i.p.InitializeInventoryInstancePlugin [ERROR] - java.lang.NoClassDefFoundError: Could not initialize class com.ibm.icu.impl.ICULocaleData
  java.lang.NoClassDefFoundError: Could not initialize class com.ibm.icu.impl.ICULocaleData
  

Desired Behavior

• An update to a current jaxen version 1.2.0 is required and the icu4j library is dropped from future releases. The icu4j library is just a transitive dependency that is imposed by the older jaxen version 1.1.1.