Made handling of quit option similar to the other actions

Moved the special handling of the quit option from the keypressed
function to its own function, the existing action-handling code will
handle the new quit function by design.

Also added a check for the up/down keypressed events to ensure that the
right-hand menu is selected before parsing the events.
Updated credits.lua
Negative money changes

Fixed trying to start playing with negative money
Fixed the initial bet amount to be 1, instead of 2 if the player only
has 1 coin. This way, negative money can't occur.
Fixed the game over check to be < 1 instead of == 0.
Fixed font size changing with quit prompt

Fixed an issue where the font size would change in the poker and
blackjack games.
Add 3 people to credits
Merge pull request #1285 from edisonout/newcredits

Update credits with new contributors
Merge pull request #1268 from Protuhj/pokerquit