Lens improvements.

[davesmith00000]

Or we should just use monocle or quicklens or something inside of games... 🤔

The Lens implementation - as crude as it is - has been entirely sufficient for scene management, but it's pretty limiting outside of that.

Two specific problems are:

1. The inability to describe an Optional lens, i.e. operating on an element if it's present.
2. Related since this could also be described as 'optional' - the lack of ability to pull things out of lists (or rather Batchs), operate on them, and put them back.