Touchy Feely & the New Line

Added in Game.isTouchScreen as a basic determination if the game is
being played on a device with a touchscreen.

ExpandTab now has onOpen and onClose events that trigger when it’s done
opening and closing respectively.

Mouser now has touch events and treats them just like clicks.

String now has the numberOfOccurences function to determine how many
time a string occurs in the string.

TextBox can now have new lines in the middle instead of just after the
end of the line and the delimiting character can be set as
endLineDelimiter.

Vector2 now has a toString function.