Add Time-based Constraints to State-based Properties

[jlink]

Testing Problem

Some expected properties of state-based systems are time-related, e.g.:

On click the button will be disabled but eventually be re-enabled again.

Suggested Solution

Add functionality similar to what Quickstrom does for Web UIs.
It's well described in this paper

Discussion

This probably requires the new state-dependent generation. See #134.
Implementation-wise this functionality could be available for any Chain or be more specific for ActionChains.

[owickstrom]

Nice to see the ideas from Quickstrom spreading! Let me know if you want to bounce some ideas, @jlink. I'll try to help as much as I can (family takes most of my time these days.)

[jlink]

Thanks @owickstrom! I'll take you up on that offer some day - hopefully not too far in the future.