Implement local time accounting

[starcraft66]

On top of the pubsub events that will be received when reservations expire, the client should have its own notion of time accounting and expire sessions without server interaction in case of network issues or creative players disconnecting the network cable "lag switch" style in order for the client to miss its session expiration message and let the user keep playing past the time limit.

This should come with message handling to add or decrease session time on the fly.

[starcraft66]

Implemented by #12