Faster keyboard interface

[KevinDCarlson]

For most logics (probably every logic so far?) there's only one cell type with any given first letter. It seems like a nicer workflow to input a Stock to just write "shift+enter, S" than to have to reach for the ctrl key, i.e. if the menu filters down to a unique element maybe it should just get picked.

[KevinDCarlson]

I didn't realize you can just hit (for instance) ctrl+F from any position to get all the way to a new flow, which makes this less important. Still think it makes sense though.

[epatters]

Also, the keybindings to create specific types of cells should even work when the new cell menu is not open.