Moving methods getCharge and getFrequentRenterPoints to Movie class.

Signed-off-by: Tomasz Kamiński <kaminski.tomasz.a@gmail.com>
Adding Price class. Adding Price subclasses for all movie types.

Signed-off-by: Tomasz Kamiński <kaminski.tomasz.a@gmail.com>
Applying Price to Movie class. Moving method getCharge to the Price
class.

Signed-off-by: Tomasz Kamiński <kaminski.tomasz.a@gmail.com>
Replacing conditional switch-case instruction by a polymorphysm.

Signed-off-by: Tomasz Kamiński <kaminski.tomasz.a@gmail.com>
moving method getFrequentRenterPoints to the Price class. Overriding it
in the NewReleasePrice class.

Signed-off-by: Tomasz Kamiński <kaminski.tomasz.a@gmail.com>