Parsing of entity type (PC versus NPC) string and int values

Also initialized tests.py to test the new parsing methods.  So far so
good.
Added validateEntityType for increased error checking on a parsed entity type

If a value is passed as an entity type for a Entity and that value
would normally be out of bounds (e.g. representing neither a PC or an
NPC) the Entity is reinitialized defaulting to be an NPC.
Merge branch 'entity'