cubicweb #3203339 Improve :eid: directive [open]

This is fine

:eid:`XXX:some text`

But when using

:eid:`XXX`

in some rest description one get an invalid link instead of either an error or the use of entity_from_eid(XXX).dc_title() of the inline view for the entity.

priorityminor
typebug
done in<not specified>
closed by<not specified>