starting the implementation of the modifier/power-up system
more modifiers work, also some templating insanity
separated object visibility and physicality from alive status

Objects can be alive but not visible and/or physical, but a dead object
should never be visible or physical.
implemented basic extra life modifier
Merge branch 'master' into power-ups
adding stubs for modifier events

not yet hooked up to anything
merged branch more-game-control

though something went kind of odd with the merge…
Merge branch 'master' into power-ups
Merge branch 'master' into power-ups
switched GameObjectCollection to using an std::list to allow more efficient object removal
added a method to prune dead objects out of GameObjectCollection
Merge branch 'master' into power-ups
partially complete paddle modifier
Merge branch 'master' into power-ups

Conflicts:
	src/core/BleepoutApp.cpp
	src/core/PlayerManager.cpp
Merge branch 'master' into power-ups
adding modifier specifiers
more modifier spec stuff, json serialization
implemented modifier spawning
Merge branch 'master' into power-ups
implemented modifier spawning, really basic rendering, etc

it needs cleanup but it works