Fixed 404 headers. REF: #1620
Fixed display of option choices when editing an option that does not use choices.
Removed redundant code from admin footer controller
Merge branch 'v1.5.6.x' of https://github.com/opencart/opencart into v1.5.6.x
Fixed hyphen problem with PayPal Express checkout url
* Changed PayPal cardissue to issuenumber variabe for PayPal Pro

REF: 1822
Used correct admin setting to check if product count should be done on a category

Close: #1828
Change log updated to include the fix for the exception error during a failed mysqli connect problem.
Merge branch 'v1.5.6.x' of https://github.com/opencart/opencart into zgv1.5.6.1