Optimize initialization process for DataTables

An initial comparison between the time it takes to create a Woodwork DataTable and a Featuretools Entity was performed using a large dataframe from the predict-next-purchase demo. If Woodwork DataTables are used to replace Featuretools Entities, the performance should be comparable.

Creating a Featuretools Entity, using `EntitySet.entity_from_dataframe` took 56 seconds. Creating a DataTable with the same input took 74 seconds (+32%). We should do performance profiling to identify the areas where Woodwork is slower, and work to improve the speed with which a DataTable can be created.