[Feature] Respect input polarities

[bkj]

Modify the DLT call to constrain coefficients to the correct polarity.

[bkj]

cc @ezekielbarnett

[ezekielbarnett]

#21

[bkj]

Running w/ this fix on the SOI test example gave weird results - magnitude of coefficients decreased from ~ 0.1 to ~ 1e-5. Seems odd, going to leave this out for now, because we can clamping to have an impact, and really small coefficients (probably?) break that.