Handles shutting down all threads when "exit" button is pressed

src/main/java/com/application/DB/DB.java

src/main/java/com/application/DB/HelpingFunctions.java

src/main/java/com/application/GUI/InputPopUpWindow.java

...main/java/com/application/GUI/LineChartFunctionality.java

src/main/java/com/application/Main.java

src/main/resources/com.application/CSS/styleSheet.css

target/classes/com.application/CSS/styleSheet.css

target/classes/com/application/DB/DB.class

target/classes/com/application/DB/HelpingFunctions.class

target/classes/com/application/GUI/InputPopUpWindow.class

.../classes/com/application/GUI/LineChartFunctionality.class

target/classes/com/application/Main$1WorkerThread.class

target/classes/com/application/Main.class