And since `Zotero.Libraries.isGroupLibrary()` just checked that
property, that hasn't worked either since `isGroup` was added in 2015.
There's no test for `.isGroup`, and the test for `isGroupLibrary()` used
`if()` instead of `it()`, so it never actually ran.
Also:
- Remove old code block in search.js that called `isGroupLibrary()`.
Since `isGroupLibrary()` didn't work, this block was unused, and its
logic was previously added elsewhere.
Also:
* _finalizeErase in Zotero.DataObject is now inheritable
* Call _initErase before starting a DB transaction
* removes Zotero.Libraries.add and Zotero.Libraries.remove (doesn't seem like this is used any more)