Units of distance in job document not clear.

[JimmyRushing]

Morphct requires that the distances are in angstrom so I checked the job document and it shows the following, which I believe is angstroms:

[chrisjonesBSU]

The screen shot doesn't show the rest of the reference values, and other values with units in the job doc, but the units for all of the other values seem to be pretty straight forward, except for ref_distance.

[JimmyRushing]

[jennyfothergill]

ref_distance is in angstroms. If you use planckton.utils.units.string_to_quantity, it'll convert that string to a unyt quantity which is really nice for doing math with units.

If you wanted to make a PR to add documentation or an example, that would be great. :)