- Add an 'exclusive' option to transactions that causes them to block other
transactions and wait for other transactions to finish before starting,
instead of nesting
- Resolve Zotero.DB.waitForTransaction() promise before returning from
executeTransaction()
- A side effect of the above: wait for a newly created item to be selected in
the middle pane and rendered in the right-hand pane before returning from
executeTransaction()
- Don't save items multiple times when adding/removing a non-final creator in
the Info pane
- Use a simpler, non-recursive method for focusing the next field in the Info
pane; this prevents "too much recursion" errors if something causes the
right-hand pane not to be rendered when expected
This fixes an issue where two transactions started around the same time
could run separately instead of nesting, causing the statements from one
to end up running not within a transaction
