#12 alternative filename for export PDF, ...

[roman]

make export files sortable by filename by allowing custom date format / using filename template like e.g. "basename-%Y-%m-%d.pdf"

timetool-export-07-Mar-2007.pdf
->
timetool-export-2007-03-07.pdf

maybe other filename options?
suggestions:
- export year/month/day
- time range year/month/day to year/month/day
- user name