Added new conversions_c module to implement all entity/player type conversions directly to the build.  Made changes in entities.helpers and players.helpers to accomodate this change.

Updated entities.entity.BaseEntity and players.entity.PlayerEntity to use conversion in place of instantiation.

Updated getting/setting of properties, keyvalues, and offsets for BaseEntity classes.

Updated players.entity.PlayerEntity to use __new__ in place of __init__ to more easily allow inheritance by other classes.

Added ServerUnknown.get_base_entity() to return the BaseEntity pointer of the entity.