Added 'fromString' method to Direction class

The method takes a string corresponding to a direction and returns
the appropriate Direction enumeration entry.
Added 'isOutside' field to the Room class

When the field is set to true, narration about the weather outside
or the time of day will be added to the description.
Initial work on universe file parsing and weather

Added to the universe class is a field that determines whether the
universe should generate and keep track of weather for the universe.

The major addition in this commit is the removal of the old default
universe and the addition of the universe file parsing code. The
server now checks for definitions of rooms and items in a YAML file
before starting the server. The format is described in part in the
"default.universe.yml" file, which is included here.