On restore, added a link to the parent deletion restore if any exists
on a cascading parent. Added a test to cover this case to ensure its shown.
Also tweaked default empty state message on recycle bin item list to align
with new column count.
Also done a little existing code cleanup including a getUrl helper on
the deletion items.
Related to #2682 & #2594
Renamed some columns to be more generic and applicable.
Removed now redundant book_id column.
Allowed nullable entity morph columns for non-entity activity.
Ran tests and made required changes.
