#256 - added database export functionality

...adlocker8/budgetmaster/controller/SettingsController.java

...in/java/de/deadlocker8/budgetmaster/entities/Account.java

...n/java/de/deadlocker8/budgetmaster/entities/Category.java

...in/java/de/deadlocker8/budgetmaster/entities/Payment.java

src/main/java/de/deadlocker8/budgetmaster/entities/Tag.java

...e/deadlocker8/budgetmaster/repeating/RepeatingOption.java

...ocker8/budgetmaster/repeating/endoption/RepeatingEnd.java

...r8/budgetmaster/repeating/modifier/RepeatingModifier.java

.../de/deadlocker8/budgetmaster/services/AccountService.java

...de/deadlocker8/budgetmaster/services/CategoryService.java

...n/java/de/deadlocker8/budgetmaster/services/Database.java

...de/deadlocker8/budgetmaster/services/DatabaseService.java

.../de/deadlocker8/budgetmaster/services/PaymentService.java

...java/de/deadlocker8/budgetmaster/services/TagService.java