BibFormat: new bfe_date parsing/formatting options
- Adds parameters to customize the parsing of the date (format, source). Source format can also be guessed provided that mx.DateTime module is installed.
- Special output of year-only dates.
Signed-off-by: Jerome Caffaro <jerome.caffaro@cern.ch>
Tested-by: Esteban J. G. Gabancho <esteban.gabancho@gmail.com>