Added Popups for Useradmin rights, Userremove from a trip and leaving a trip

...p/src/main/java/com/example/mobileapp/MemberFragment.java

...ava/com/example/mobileapp/Recycler_View_Adapter_User.java

...main/java/com/example/mobileapp/Trip_Overview_Screen.java

Frontend/app/src/main/res/drawable/scrollbar.xml

...end/app/src/main/res/layout/fragment_member_fragement.xml

...pp/src/main/res/layout/fragment_transaction_fragement.xml

Frontend/app/src/main/res/layout/layout_trip.xml

Frontend/app/src/main/res/layout/single_trip.xml

Frontend/app/src/main/res/layout/trip_main_screen.xml

Frontend/app/src/main/res/values/styles.xml