A_06

Added two new Wall types:
+ Eye: can only be attached to something else on the left or right, only
stacks vertically (or in horizontal pairs), and will not allow the
player to grab the wall.  He can still use wallclimb if he has the
momentum, though.
+ Platform: The player can pass through it while travelling upwards,
they can drop back down by crouching or using air drop (Warning!  using
air drop WILL force you to fall through!)

* Changed crouching and airdrop variables in the Player class to be
public, for the boundary testing
* Updated the test level
+ Added print lines to give some visual feedback to what's going on
while the level loads
+ Added Boundary class to store the boundary itself and any special
modifiers (such as slidable and dropthrough)