Fixed #82 - backup database to client

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

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

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

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

src/de/deadlocker8/budgetmasterserver/main/Database.java

...deadlocker8/budgetmasterserver/main/DatabaseExporter.java

...deadlocker8/budgetmasterserver/main/DatabaseImporter.java

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

...r8/budgetmasterserver/server/database/DatabaseExport.java

...r8/budgetmasterserver/server/database/DatabaseImport.java