Include tables for keeping track of games and clues

In order for users to be able to keep track of games and clues that have previously been encountered - including statistics for these games/clues as well as assigned topics for clues - four additional tables are now created in the database (clues, which keeps track of the clues; clue_scores, which keeps track of how well each user answered each clue; games_scores, which keeps track of scores for each round played; and topics, which keeps track of user-defined topic names).

- Wrote an install.php file that automatically creates all database tables, which include the four listed above, and the users table.
- Added an additional dimension in the clues array in JavaScript to keep track of whether the user got a clue right or wrong (or whether he/she passed on it).
- At the end of each game (i.e., round), a new PHP script called updateprogress.php is invoked to update the above database tables based on the performance of the user.