Less lossy processing

[inakaboy]

Various changes to reduce the chance that a user would lose data if they exported media files, processed them with this tool and then deleted the takeout files after making use of the processed files.

The main changes are:

• Files with an unsupported extension or for which a JSON sidecar could not be found are now moved to the errors directory so the user can manually inspect them.
• More detailed log messages (could be a bit cleaner but I tried to preserve the original logging as well).
• Added some additional patterns that were causing my motion photo MP4s' JSON sidecars to not be found.
• Added .webp, .dng, and .m4v to the supported files list because I had some files of these formats in my google photos export.

(sorry for all the random commits; I was editing directly in Github....)