Use exclusively `date` field instead of both `date` and `year`

[Carlos-M-D]

Hi,

Thank you for creating this useful app. I noticed that it currently uses both date and year fields for managing literature entries. However, according to the biblatex documentation, it is better to exclusively use the date field instead of year:

The year of publication. This field is a literal field only when given explicitly in the data (for plain BibTeX compatibility for example). It is however better to use the date field as this is compatible with plain years too and supports many more features (p. 27).

If there is no date field in an entry, biblatex will also consider the fields year and month for backwards compatibility with traditional BibTeX but this is not encouraged as explicit year and month are not parsed for date meta-information markers or times and are used as-is (p. 40).

Using both date and year fields may cause parsing issues in some literature managing environments such as Emacs' bib mode. Therefore, I suggest using exclusively the date field for managing literature entries.

Thank you.