#546 - import/export database: import and export template groups too

.../deadlocker8/budgetmaster/database/DatabaseParser_v8.java

...de/deadlocker8/budgetmaster/database/DatabaseService.java

...e/deadlocker8/budgetmaster/database/InternalDatabase.java

...ster/database/model/converter/TemplateGroupConverter.java

...er8/budgetmaster/database/model/v7/BackupDatabase_v7.java

...er8/budgetmaster/database/model/v8/BackupDatabase_v8.java

...udgetmaster/database/model/v8/BackupTemplateGroup_v8.java

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

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

src/test/resources/DatabaseParser_v8Test.json