Decide how to handle different units

[ericboucher]

It looks like HUI and Vesta are using different metrics for Turbidity and NNN.
We need to decide what unit we are using internally and make sure to convert metrics when needed.
We changed the units shown as part of #966 since HUI is the only active table. If other groups are using water sampling metrics again, we will need to update/convert the data.

[Caesarh97]

Vesta has not uploaded anything to Aqualink, as far as I know, so I think we should go for HUI's units for now.