The 2.0-beta MSSyncContextDataSource includes an optional method signature for
"-(NSUInteger) systemPropetiesForTable:(NSString *)table;"
Should be "Properties":
/// Returns the MSSystemProperties that should be stored locally (example: __createdAt, __updatedAt)
/// If not implemented, the default of __version will be asked for from the server
-(NSUInteger) systemPropetiesForTable:(NSString *)table;