Adding leaf wetness to measurement type and leaf surface wetness as measurement type.

[kersting]

Is your feature request related to a problem? Please describe.
Some power performance test towers include leaf wetness sensors. The current model does not have such variable.

Describe the solution you'd like
Add leaf wetness as sensor_type and leaf_surface_wetness as measurement_type

Describe alternatives you've considered
I couldn't find any alternatives in the data model, but I'm open for suggestions.

Additional context
Sensor primarily used for power performance test. Here you can find one example https://metergroup.com/products/phytos-31/