Add Debug Option

[bupp925]

https://github.com/SearchSpring/magento2-searchspring-feed/blob/master/Helper/Generator.php#L218

When debugging certain data issues, it'd be very helpful to be able to pass a single Entity ID as an option in the regen script, rather than having this to comment on/off - the way it is, this runs the risk of forgetting to uncomment the line, which I know has happened before.

In a perfect world, this &debug=12345 option would dump a JSON object of the data record directly to the regen screen in browser, bypassing any need to update a test feed file.

[shrekked]

@julesbravo @bupp925 In addition to passing an entity ID, it would also be nice to output debug statements based on the current page parameter.

Reason being, Magento's product database frequently seems to have corruptions which cause a 500 error when we try and request product attributes for specific products, this prevents us from even knowing which entity ID is causing the issue.

If we had the ability to add a debug statement that output the entity ID(s) contained within the current product collection before fetching product attributes, this would allow us to quickly and easily determine which products are corrupt and causing the regen to fail.