Improved memory management for large query sets.

[c-harris]

Another issue that @kirill533 shed light on in issue #240 related to podata not being very memory friendly for large query sets. He attempted to solve the issue at
kirill533@99caf30

But had some issues related to expansion.

I would propose that if we change the interface at

POData/src/POData/Providers/Query/QueryResult.php

Line 16 in 241d309

public $results;

to be a iterator (generator)

And

POData/src/POData/ObjectModel/ODataFeed.php

Line 47 in 241d309

public $entries = [];

would also need to be a iterator (generator)

It would then allow for the data to be loaded in a more dynamic nature to better suite. Smaller datasets and tests could just use the ArrayIterator Class to maintain simplicity for those a not sending thouands of records.