Float windows by default when there is no bundle identifier

[Bogdanp]

Is your feature request related to a problem? Please describe.

Often, when I'm developing small GUIs for local use (eg. in Racket), I'd like for them to be floating. But, they're not "proper" Mac apps so they don't have bundle identifiers, which means I have no way to configure Amethyst to default to floating them.

Describe the solution you'd like

Basically, this change. I'd be happy to make a PR if this seems reasonable. If desired, we could make this a configuration option.

[DanielRoeven]

Just popping in to say that I'd love this feature / preference / default too 👍