Fix error on deleting of return status

https://github.com/opencart/opencart/pull/975
Removed duplicate entry_customer_group

https://github.com/opencart/opencart/pull/975
Fixed cache delete when adding new language

https://github.com/opencart/opencart/commit/0223f66cdeb0a9b0468516ff291902a27f649b8b
Closes #48 additional DB table indexes
Whitespace standardization

See https://github.com/blog/967-github-secrets for viewing commits
without whitespace differences
Removed 'type' from image cache filename

Cached resized images should now match admin in all instances
https://github.com/opencart-ce/opencart-ce/blob/2bca5efa2090e5bc2a7159821819fe2082859f72/upload/admin/model/tool/image.php#L13
Revert "Removed 'type' from image cache filename"

This reverts commit 74dcebc6d83e70f167e54267a4eb830e9edba5d8.
Minor alignment correction
Spelling corrections
Additional DB table indexes
Correct coupon valid total test

Coupon will now be active when cart total greater or equal to the coupon
total field. This now matches the help text and documentation.

https://github.com/opencart/opencart/issues/966
Array to string conversion error for GET path

Some PCI scanners will test for this.  We may want to validate other GET
parameters that are passed back to the URL in the future though this may
cause problems for some mods that use them as markers.
Remove install CSS reference to nonexistent image

https://github.com/opencart/opencart/commit/58645e841a84d5140fdba63c6caf0c3a652e7089
Small fix for mail class

https://github.com/opencart/opencart/commit/48bf9a005dbc7d8aab427e1b7bcb8294da2f7b96#diff-2
Remove sprintf from forgotten mail message

https://github.com/opencart/opencart/pull/1019
Remove alt attribute from links

https://github.com/opencart/opencart/issues/955
Improve white space match product search

https://github.com/opencart/opencart/issues/1034
Check coupon discount is not greater than total

This improves the situation where reward points and a coupon is use on
the same order.
https://github.com/opencart/opencart/issues/937

https://github.com/opencart/opencart/commit/e0ccfc86967cb309d8618f1f5f8eccb4058891dc
Undefined index errors when validating reviews

Caused by bots trying to spam product reviews
Only write reviews when reviews are enabled