Include lat-lon info for salt field in netcdf
Add API endpoint for retrieving salt frames
Add Models.saltFrameSource and accompanying API calls to client
It's now a frame source, not a vector frame source
Try harder to round floats in json objects
Provide an API endpoint for salinity contours
Check that callbacks exist before calling them
Teach MapView how to display salinty contours
Genericise some overly verbose variable names
Switch to contour plotting!
Try logspace contour levels... hideous
Fix borked levels calculation. Slightly better. Still hideous.
Expose the number of contour levels used in THREDDSFrameSource.salt_frame
Add support for numSaltLevels query parameter
Show the number of contour levels being used in the TABSControl
Pass config objects to the with.*Frame functions instead of multiple params
Prefer using `self` over `this`
Fixup json error in salt frame responses
Fix velocity field stuff after changing API
Go back to linear space for contour lines