Fixed bug in 'Input' class involving mouse visibility.
Some tweaks to 'Input' class, some renaming and reorganization of input handling methods in 'GameLoop' class.
Improvements to music and sound handling:  (1)-Game no longer crashes if no audio device is found.  (2)-Menu song, '404 error', restarts upon returning to the main menu.  (3)-New 'Audio' class and global 'AUDIO' instance of it.
Moved handling of 'EXIT' input to inside of the 'Input' class.  Now 'Esc' key exits the game on the title screen as well as in-game.
The current time is now printed to console when a new song begins playing.
Changes to 'OptionsPage' class:  (1)-Enabled buttons are now black text on dark red background; disabled buttons are same as before (dark red text on black).  (2)-Buttons change to enabled/disabled color schemes when appropriate.