downward motion to space invaders
temporary hack to work around model scale data corruption
tweak modelScale to 2.0 for better space invaders
add sounds to space invaders
change game at for space invaders to be close to avatar
Merge pull request #1854 from ZappoMan/invaders_tweaks

Invaders tweaks
Merge branch 'master' of https://github.com/worklist/hifi into scripting

Conflicts:
	examples/spaceInvadersExample.js
	interface/src/ParticleTreeRenderer.cpp