Homematic: Changed alive validation check, Homegear variable bugfix and state invert for HM-SCI-3-FM

I changed this intentionally to one minute. This is only the interval for the connection check, it should run fixed every minute. The alive interval to mark a connection as stale is still configurable in openhab.cfg (homematic:alive.interval)

I think users get's confused if they should configure two interval properties.

Reason for this change: https://groups.google.com/d/msg/openhab/9_hYgzn_-qo/4FwSQkVYTC4J