Implementation of UITableViewDataSource which allows multiple child UITableViewDataSource implementations to be composed together and presented to a UITableView as if they were a single data source.
Useful in situations where you want a single table view to present content from multiple sources and you want to keep the logic for those data sources separate.
Wraps up the logic to dispatch a given protocol method call to the appropriate child datasource as well as offsetting passed/returned section indexes and aggregating results across child data source methods.