feat: implemented group chat

...rc/main/java/unipotsdam/gf/interfaces/ICommunication.java

...src/main/java/unipotsdam/gf/interfaces/IGroupFinding.java

...f/modules/communication/service/CommunicationService.java

.../src/main/java/unipotsdam/gf/modules/group/GroupView.java

...in/java/unipotsdam/gf/modules/group/GroupfindingImpl.java

...ain/java/unipotsdam/gf/process/GroupFormationProcess.java

...schen/src/main/java/unipotsdam/gf/taglibs/ChatWindow.java

...forschen/src/main/webapp/groupfinding/css/edit-groups.css

...nsamforschen/src/main/webapp/groupfinding/edit-groups.jsp

...amforschen/src/main/webapp/groupfinding/js/edit-groups.js

gemeinsamforschen/src/main/webapp/project/tasks-student.jsp