added validation to cost and weight fields in the Item model in models.py
In models.py
added a couple of TODO comments
added encumberance_penalty derived field on character model
In models.py
fixed total weight and total value calculations for a character's items
added validation to Possession quantity field
In models.py
added total_points_in_skills field to character model
In models.py
added total_points_in_spells field on character model