Added initial content resources, skeleton for layouts, and basic classes.

Added names of attributes, starting classes, weapons, armor, rings,
items.
Also added starting attributes from the Network Test (will need to be
updated when the game releases).
Created Attributes class to store and manage the attribute values.
Created CharSheet class to encapsulate all the information about a
single character.
Created StartingClass enum, each value of which contains its resource
key which can be used to access the starting attribute values.