refs #6444 when copy a php file check whether it was actually copied and whether they have same content. Wondering about problems re using different filesystems for tmp and other directories and whether opcache causes any problems but should not
refs #6444 if it fails to copy the first time, try it another time before triggering the error
Merge pull request #6445 from piwik/fileCopyCheck

Check if a file was actually copied when copying a file