Beta upgrades: player ship complete!

Main element for this update is the new player ship, the Mantle. This
ship is heavily armed, invulnerable, and uses its own geometric style.
Its structure is fluid, allowing it to sweep gracefully through space.

Other changes include:

Time governor tick has been hard-coded to 2, rather than a clock-read
tick. This may introduce uneven animation, but it ensures even
distribution of motion blur across the screen.

Render compositor/shader now has independent screenWarpScale and
chromatic aberration properties, allowing Processing-side adjustment of
the refraction systems.

Numerous tweaks to refraction levels. In particular, cloaking device is
now much more pronounced.

Type-B turrets now reconfigure their base sprite assets to Mantle
geometry.

Missiles are fast again, and have refractive exhaust like other vessels.
Steering fixed to use correct maneuver jets on both sides. Still can't
hit for beans. Working as intended.

Variation in background dust scale.

New DEV program: renderout_spritesWithAlpha.pde. Because my Maya
workflow produces several passes without alphas, I've been editing them
by hand, but with so many sprites that was impractical. This code takes
a filename stub, loads in a mask file plus diffuse and normal passes,
trims the diffuse and normal passes to have correct alpha, and generates
a warp map from the normal pass. The latter is by far the most
time-consuming. It does not trim the dimensions of the sprites; that
must still be done by hand, for now.