*Added a contact abstract class that serves as a superclass for user and
group
* Added a group class
* Updated persistenceManager to fit the new contact system.
* Updated all classes that used methods, that were updated.
* added package- and module-info.java, changed JRE from 8 to 11
* moved ObjectProcessor into the processors package
Co-authored-by: CyB3RC0nN0R <kske@outlook.de>