The create-new button will be used for list views that allow an item
of the same type as the list to be created (project, branches, tags,
etc).
Whether or not the create-new should be shown is up to the parent of
gr-list-view, as it depends on account capabilities that it is aware of
and varies per list.
The modal is included in <content></content> the same way that the table
is, as it also varies per list view type. The IDs and events fired must
be constant across list views implementing this.
Change-Id: Ifb76cb47867389dafcca5775d00d117d8e321f53
6fca6be8c9