new payments can now be saved into database

src/de/deadlocker8/budgetmaster/logic/Helpers.java

src/de/deadlocker8/budgetmaster/logic/Payment.java

src/de/deadlocker8/budgetmaster/logic/ServerConnection.java

src/de/deadlocker8/budgetmaster/ui/NewPaymentController.java

src/de/deadlocker8/budgetmaster/ui/PaymentController.java

src/de/deadlocker8/budgetmaster/ui/PaymentTab.fxml

...deadlocker8/budgetmaster/ui/cells/CategoryBudgetCell.java

src/de/deadlocker8/budgetmaster/ui/cells/PaymentCell.java

.../deadlocker8/budgetmasterserver/main/DatabaseHandler.java

...de/deadlocker8/budgetmasterserver/server/SparkServer.java