Werk #17262: Support Diagnostics: More detailled list of site's files

The file "filesize.csv" contains a list of all files insided a site. It is always included in the dump. From now on, it has additional columns:

Before: * size * file path

Now: * size (in Bytes) * file path * owner * group * mode (the file's access rights) * changed (the date/time of the last content change)

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