Test performance of saving individual squares in different IndexedDB keys

[aivuk]

In the future we would like to have squares reuse across different boards, as templates squares or to make it easier for content sharing. I see to architectural approaches to this:

• Every is square is have a key entry on Indexed DB.
• We have a Map in a Indexed DB entry with a key as "squares". The advantages in this approach is that it would be easier to make queries around all the squares.