Beta upgrades: performance tweaks

Numerous upgrades to boost performance, including:

loadImageScaled function, replacing the high-res assets on disk with
lower-res assets in memory according to a specified scale function. New
diagnostics indicate that resolution matters, so I'm dropping it to only
a necessary res.

New keyboard command: "N" restarts the program, toggling between full
and half resolution in case speed is really necessary. The results
aren't too nice, but at least it's an option.

Tweaked main scene lights. They're very nice now.

Lights now set a specularFactor, which multiplies specular shading. This
makes for much nicer highlights.

Lights were discovered to be a serious contributor to frame rate. I've
reduced the diameter and instated a new stencil, which has noticeable
results while retaining quality.

Reinstated low-res buffers in RenderManager; warp maps don't need much
res.

Tweaked bloom power from 3.0 to 4.0, resulting in cleaner geometry
outside flare spots.

Tweaks to Ships to preserve good lighting strength from all light
sources.