Move Pokemon classes to pokemon subpackage
Change Ability from class to interface
Add SpeciesRepository

This interface will be used for loading the species from a storage
device. This can be an XML file, a SQL database, or any other form of
storage.
Rename maxPP to pp for proper terminology
Format exception string
Add isInCombat method to Trainer class

This method is being added in anticipation for any future need.
Add Client to Player