Generic Magnetic Thing

A magnetic thing is one which is attracted to its home room. After it is picked up, it checks once each time_interval whether it has been touched in any way during the interval. A magnetic thing is touched whenever some verb tells it that it is. This way, you can have a thing which goes home if it is picked up and not used for some period of time. The time_interval is given in seconds. Setting it negative will demagnetize the object.