(see Desc) Code Reorganization

Looked over the source and reorganized some things.
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[] New Files []
(*) Moved Category::Type into its own file
(*) Moved struct Command into its own filepair
(*) Moved derivedAction() into Command.h
(*) Moved CommandQueue into its own filepair
(*) Moved SpriteNode into its own filepair
(*) Moved main() into its own file
(*) Added drawChildren() to SceneNode.h/cpp
(see Desc) Code Reorganization pt 2

Import changes
Minor Comment Changes
Rearranged Galaga.h/cpp function order (should now match call order)
Galaga.h/cpp PlayerSpeed and TimePerFrame are now const & static
Revert "(see Desc) Code Reorganization pt 2"

This reverts commit 07cd91bf7b4fd7b004274af83b1ff58469df8f4b.
Revert "(see Desc) Code Reorganization"

This reverts commit 491e2bed2da30d7ac46830c15fbea659821e51d4.
PlayerSpeed is now static & const