Custom "How to cite"

[mauromsl]

Is your feature request related to a problem? Please describe.
Add support for customizing the How to cite section

Describe the solution you'd like
A free-form textbox where users can add their own custom "how to cite" block when the one generated from Janeway is not suitable. If such field is present in an article, we render it, otherwise we render the current auto-generated one.

Describe alternatives you've considered
Allow editors to use a regex/template to create their own patterns for the how to cite block. This might not be a very user friendly approach, perhaps something we can add later as a separate feature