Added some User select/update functionality

1. Added index(), store(), and show() functionality to UserResource.
2. Corrected issue with wrong observer set in User model.
3. Added all functionality to UserRepository, and updated interface to
match.
4. Added class PostSqlMapper to handle conversion of POST input to SQL
input.
5. Updated BaseLaravelValidator with needed functionality.
6. Added all functionality to validation observer for User model.
7. Added all functionality to UserValidator.
8. Updated ValidatorFactory to use InternalException instead of base
Exception class.