Add additional notification options to the Game Settings.

Concise description:
Add additional notification option to the Game Settings.
Notify me when:
This will improve the following aspects of the site:
Add additional notification option to the Game Settings.
Notify me when:
- It's my turn in a casual game and i have less than 6 hours remaining to play (by email)
- It's my turn in a casual game and i missed my previous turn (by email)
This will improve the following aspects of the site:
- it will reduce deadbeating with out cluttering up a person's email inbox with cc notifications