NPC Patrol Paths

It's now possible to create paths within the scene .xml for a level for
NPCs within that level to follow.

The new PatrolPath class stores a vector of Ogre::Vector3s representing
nodes along the path; the NPC will move from one node to the next,
looping back to the first node upon reaching the end.

Path nodes are represented in the scene .xml by objects named
"PatrolPath.[PathName].[NodeIndex]", where [PathName] is the name of the
path to which the node belongs and [NodeIndex] is the node's index
position within the path, beginning at 0.

Character names in the scene .xml are now in the format
"Character.[CharName].PatrolPath.[PathName].[uniqueID]"; where
"Character" and [CharName] are required fields, "PatrolPath" and [PathName] refer to the Path the character follows (if any), and [uniqueID]'s purpose is unchanged.