Add PackXYZFloatFrom16 output formatter for TYPE_XYZ_FLT.

Transforms created with TYPE_XYZ_FLT would otherwise result in XYZ
values that were off (too small) by a factor of 2.
Add UnrollXYZFloatTo16 input formatter for TYPE_XYZ_FLT.

Transforms created with TYPE_XYZ_FLT would otherwise result in XYZ
values that were off (too small) by a factor of 2.

This change fixes the testbed based on my last commit.
Merge pull request #25 from patricknoffke/master

- Add PackXYZFloatFrom16 output formatter for TYPE_XYZ_FLT.
Looks good. Thank you!