server: fix time for heartbeats to every 30s

previous timeout was set to 500ms, heartbeats to 6, meaning one hartbeat every 3 sec
changed these values to send one heartbeat only every 30 sec
server: use force delay by default, to make computer moves last at least 800ms

on fast computers, having the computer place as fast as possible, is annoying.
use a forced delay, if the computer is faster than 800ms.

can be turned on in dedicated server by passing --no-delay option