Add year of document release to numbering scheme

[bkimminich]

While I found a clash of the numbering scheme of OWASP Top 10 and the API Top 10 (OWASP/API-Security#24) I accidentially realized that the Docker Top 10 lack the year of release in their numbering scheme.

Recommendation

Use D1:2019 instead of D1 in the summary table and when referring to individual list entries. This would harmonize Top 10 lists of OWASP overall a bit.

[drwetter]

Ok, let's talk today or tomorrow in person about that. Note there's currently a two digit number after the leading D otherwise the automatic sorting for PDF generation wouldn't work

[drwetter]

IN order to avoid confusion with other projects and enable linking across projects: Once we're ready we will add this