Add `FlxGroup#killAll()` and `FlxGroup#reviveAll()`#185

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IQAndreas wants to merge 2 commits intoFlixelCommunity:devfrom

IQAndreas-testprojects:add-flxgroup-killall

Commits on Oct 22, 2013

Add `FlxGroup#killAll()` and `FlxGroup#reviveAll()`
IQAndreas
committed
Update the ASDoc in `FlxBasic` to point out the `kill` and `revive` behaviors of `FlxGroup`
IQAndreas
committed