If a references list node is selected, open the dialog to edit it.
Otherwise just insert the references list for the default group, since
this is what the user wants to do in 99% of cases.
* Replaced the simple 'referencesList' command (which opened the dialog)
with a custom implementation in ve.ui.MWReferencesListCommand, which
inserts the references list or opens the dialog like before.
* Removed the ability to insert a references list from
ve.ui.MWReferencesListDialog, since it should now never open without
a references list selected. If it does, throw an error.
I considered the behavior of always showing the dialog if there is at
least one references list already in the document, but I think it would
be confusing if the tool behaved differently depending on the state of
the document (rather than merely current selection).
Bug: T71727
Change-Id: Ifbbfa28548de9c0435c5174fb7762079f59bac54
