v0.3: Better hints, smoother gameplay

This is a general set of improvements to the hinting in the game, showing players what to do, reporting scores and cleaning up a few technical issues which were bugging me.

Gameplay improvements:

Flashing instructions now show first-time players where to move and how to open the classroom doors

• After entering a name or initials, green arrows on the floor guide the player to the 3D printer.
• The word GUN is now on the board - you can make BUN, BUG and others if you want to.
• When you have a valid (printable) word on the board, the button is indicated quite clearly

• When you print a thing which can shoot, hints come up showing you where to shoot for challenges

Technical improvements:

• Particle systems cleaned up to work better in VR and eject in a narrower cone (just looks better)
• Audio system improvements (fewer audio sources in scene, some volume adjustments)

Thanks!