Create class for common synced settings
Fixed: #176 Settings: updated, created and deleted have to be a long not an integer
Add SyncSettingItem in Account and remove common variables
Add SyncSettingItem in DropServer  and remove common variables
Add SyncSettingItem in Identity and remove common variables
Add SyncSettingItem in StorageServer and remove common variables
Add SyncSettingItem in StorageVolume and remove common variables
Update test