Add edd_get_discount_by() function
Added discount lookup by ID and name
Replace edd_get_discount() with edd_get_discount_by('id')
Fix Pippin's issues
Add edd_get_download_by() function
Add edd_get_payment_by() function
Run $field through strtolower()
Add SKU to edd_get_download_by()
Merge branch 'issue/2123' of github.com:ghost1227/Easy-Digital-Downloads into ghost1227-issue/2123
Cleanup and better validation for edd_get_*_by() functions. #2126