Right-clicking a row should have an "Add row" option to insert mid-table

[timwis]

Option A

1. Send an empty insert to the server to get back its primary key.
2. Insert that new row into the expected spot in the rows state (when the user refreshes, it will appear at the bottom but that's probably okay)
3. Wait until the server responds before rendering, to eliminate the race condition of the user editing the row before a primary key is established

Option B

1. Create a row in the state that has a special key, like _new: true
2. When saving, check for that special key and do an insert instead