Change window title
Add set_has_collided_with_paddle
Don't override default update

Base method updates modifiers
Update modifiers + improved copy ctor

Copy constructor still doesn't clone modifiers (i.e. they point to the
same mod)
Use pointers instead of references
Add modifier when paddle collides with bubble

add_random_mod_to_paddle always adds the default width modifier (the
only mod existing ATM)
Use static_cast
Testing different settings