Review existing ODK form and data validation / cleaning

[dave-mills]

• List out validation items from R that should be included in the ODK.
• Add those checks into ODK.
• Review the ODK form to identify further soft/hard checks that can be added (and list them out)
• Add them into ODK.

[dave-mills]

I'm currently working on updates to the ODK form to remove the ProSoils-specific parts and add a better way of handling the location levels. I'll bring that version into this repo soon.