Reduce LOGBOOK_DEFAULT_DELAY from 4 to 1 second.

ScenarioEventHandler only checks for events once every 3 seconds, which means that in the worst case the user waits 7 seconds before the logbook is shown. Reducing the logbook delay to 1 second makes the worst case delay be 4 seconds, which seems more reasonable.
Merge pull request #2101 from unknown-horizons/delay

Reduce LOGBOOK_DEFAULT_DELAY from 4 to 1 second.