Refactor output filename generation.
Refactor validateMLTXML() into sub-routines.
Fix bug in MltXmlReader not resetting the files array between jobs.
Fix a bug in calculating file MD5 hash when file size between 1 and 2 MB.
Reset file's status error bit when redoing a validation job.
Improve rewritten Kdenlive MLT XML file with correct proxy media metadata.

Also, remove incorrect but unneeded metadata such as kdenlive
metaproperty elements on audio and video files and mlt meta properties.