Adjusted window position

Moved windows slitghlty higher so they don't intersect with platforms.
PlayerControl does not report onGround true when on a ghost

onGround now explicitly checks for whether a found object is a
PhysicsGhostObject, and if so does not report onGround() as true.
Improved the level

Added two kinds of chunks with fireballs flying at the player. Added a
starting area of long, unbroken platform. Adjusted player speed and
platform distances.
Merging in changes from Level-generator-development

Effectively a rebase; some loose changes to master were made while I
was working on the level generation in another, private, branch.