Added Trip_Layout and implemented Tab function

Frontend/app/build.gradle

Frontend/app/src/main/AndroidManifest.xml

.../src/main/java/com/example/mobileapp/MemberFragement.java

...ain/java/com/example/mobileapp/Recycler_View_Adapter.java

.../app/src/main/java/com/example/mobileapp/Single_Trip.java

...app/src/main/java/com/example/mobileapp/Start_Screen.java

...main/java/com/example/mobileapp/TransactionFragement.java

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

Frontend/app/src/main/res/drawable-hdpi/add_button.png

Frontend/app/src/main/res/drawable-hdpi/notification.png

Frontend/app/src/main/res/drawable-hdpi/settings.png

Frontend/app/src/main/res/drawable-hdpi/transaction_bill.png

Frontend/app/src/main/res/drawable-mdpi/add_button.png

Frontend/app/src/main/res/drawable-mdpi/notification.png

Frontend/app/src/main/res/drawable-mdpi/settings.png

Frontend/app/src/main/res/drawable-mdpi/transaction_bill.png

Frontend/app/src/main/res/drawable-xhdpi/add_button.png

Frontend/app/src/main/res/drawable-xhdpi/notification.png

Frontend/app/src/main/res/drawable-xhdpi/settings.png

...tend/app/src/main/res/drawable-xhdpi/transaction_bill.png