Remove factory functions.

Not necessary anymore.
Add initial HUD bits.
Add <array>.
Track HUD elements separately.
Explain why AttachView is commented-out.
Make Container::display available to subclasses.
Check HUD visibility before rendering.
Implement initial HUD element support.
Move fuel gauge into modular HUD.
Add ShrinkWrap().
Allow Vec2 to be added to Vec3.
Indicate low fuel.

This matches the color used in Observer.
Change background on low fuel.

This matches the original Observer.
Move speedometer into modular HUD.
Include <array>.
Add move assignment for Viewport.

This fixes compilation with libstdc++.
Fix typo.
Add HUD to test lab.

This is to make it easier to test the layout bits.
Merge branch 'rulebook' into modular-hud

Conflicts:
	engine/Display/Vec.h
	engine/engine.vcxproj.filters
Don't allow layout flags on HUD decor.