#764 - include new property "endDate" in backup and restore

...dgetmaster/database/model/converter/AccountConverter.java

...r8/budgetmaster/database/model/v11/BackupAccount_v11.java

...ker8/budgetmaster/database/model/v7/BackupAccount_v7.java

...ocker8/budgetmaster/unit/database/DatabaseExportTest.java

...r8/budgetmaster/unit/database/DatabaseParser_v11Test.java

...locker8/budgetmaster/unit/database/ImportServiceTest.java

...sterServer/src/test/resources/DatabaseParser_v11Test.json

BudgetMasterServer/src/test/resources/ImportServiceTest.json