Added stuff, read description.

main.cpp:
- just using a DatabaseTester instance for testing (temporary)
- no changes will be made to this file in final version of Database

Database:
- this class is becoming more generic and extendable
- thinking about making this a singleton

PlayerDatabase:
- this is the main database class our game will use
- it has an instance of the Database class
- used to get and update player stats
- total kills
- total deaths
- total assists
- possibly going to add more
- update methods have not been created yet

DatabaseTester:
- mostly just for testing the database at the moment
- will not be used in final version