Added getUsersInGroup
Fixes. Mainscreen still a little bit defect
Merge branch 'master' of https://github.com/Gruppe01/EXPHIL03 into all-finalfixes

Conflicts:
	src/gui/MainScreen.java
Merge branch 'master' of https://github.com/Gruppe01/EXPHIL03 into all-finalfixes

Conflicts:
	src/gui/MainScreen.java
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#	modified:   src/gui/AddExternal.java
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#	modified:   src/gui/EditMembers.java
#	modified:   src/gui/MainScreen.java
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