Initial clerk implementation for validating and creating a Return
Completed functionality for creating a return and return_item entry
Also check for qty already returned for an item so a customer can't return a higher qty than the amount purchased
Merge branch 'master' into rocky.clerk

Conflicts:
	connect.js
Added updating of item stock after returning an item
Integrated makePurchase with clerk instore purchase
Made UI for instore purchase look consistent with online purchase
Added check for valid UPC

TODO: Still need to make the process return UI look nice/consistent with rest of page
Made process return page look better with some css changes
Fixed issue with verifying valid upc when passed in as string vs number

TODO: Get background color on table rows for process return page