Fix for image manager issue caused by the new UTF8.php helper update.

Added check for length.
Allow array to be written to log file.

Updated change log to include current changes on 1563 branch.
Check uploaded files for php content, reduce the risk of image files containing php and running on insecure servers.
Fixed report for coupons to search the history table instead
Removed check to allow php files through file upload if they are in the allowed list. PHP are never allowed.
Updated changelog.md with new updates and commits for 1.5.6.3 release.
Updated version number to remove the RC part.