Replace year and month in Biblatex entry examples with date

[hochleitner]

Section 2.3.9 of the Biblatex Manual states:

The fields year and month are still supported by biblatex, but the full set of date features (day and time precision, ranges, …) can only be used with date. It is therefore recommended to prefer date over year and month unless backwards compatibility of the bib file with classical BibTeX is required.

I, therefore, suggest replacing all occurrences of year and month in the examples in HgbThesisTutorial in section 6.3 and in the bib file with date. If there are no objections, I'll proceed with this (if there are any, please comment below).

[imagingbook]

No objections here. I suppose most publishers still use the traditional scheme for compatibility reasons (and will do so for some time). I have not tested this, but as long as the old format still works with biblatex we should be OK.

[hochleitner]

Alright. I've started working on the bibliography. I'll replace some other fields as well, e.g., langid instead of hyphenation with the value ngerman instead of german (to ensure the hyphenation rules of the Neue Deutsche Rechtschreibung). I'll also add some information as the eventdate field for @inproceeding and will replace @techreport with the more generic @report

Current progress is available in the biblatex-fields-update branch. I'll create a PR once I'm done.