Restrictions on citations

[mbakeranalecta]

Currently there are restictions on citations as follows:

• A blockquote can only have one citations
• It is not clear if a phrase can have more than one
• Most blocks cannot have a citation at all.

While these restrictions all match common use cases for citations. it is not clear to me why they should be restricted like that at the language level. Such restrictions could be imposed at the schema level if desired. But why not allow citations everywhere? Leave it to people to figure out if they have a reasonable use case for them.

[mbakeranalecta]

Addressed in eaf3caf9a93f5d3ddc403c5679fcd63bb7983b92