Allow to change default filename date format

[ekateiva]

This package is helpful not only if you want to open the mail preview immediately, but also to use a default mail driver locally (without preview links popup), keep the files for a day and open when needed. However, for this purpose, the default u (microseconds) date format is not very convenient (also, you can't sort by microseconds).
When the files are kept for longer time, it's easier to sort them by date format like Y-m-d_His. This change would allow users to choose the format they want to.

E.g.

vs

Also, it's backward compatible, even if users do not update their config file as I used ?? 'u' - the old 'microseconds' format implementation.

Besides that, maybe a better default option would be to use U format, as the timestamp is at least sortable:

u | Microseconds. Note that date() will always generate 000000 since it takes an int parameter, whereas DateTime::format() does support microseconds if DateTime was created with microseconds.
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U | Seconds since the Unix Epoch (January 1 1970 00:00:00 GMT)

[freekmurze]

Thanks!