Add "needs soil functional variability" parameter to soil ID list

[paulschreiber]

Add a "needs soil functional variability" parameter to soil ID list function. This information is only needed on site creation, not on every location lookup.

Not doing this work sill speed up the calculation.

[garobrik]

i'm not sure from the perspective of the backend/mobile client that we would ever want to have this parameter be set to false? as far as i understand it won't make a huge impact on the calculation speed, but it will require the algorithm to run twice. so (assuming we're caching the output of list_soils, which is seeming necessary for capri) it'd change us from a user flow something like:

• tap location on map, wait 5s for result
• create site and input data, wait 1s for further results
  to:
• tap location on map, wait 4.5s for result
• create site and input data, wait 4.5s for further results