Fix reading netcdf generated from FA file

[sandorkertesz]

This PR fixes the following NetCDF problems:

• fix issue when fields were assigned to variables without lat-lon/x-y dimensions
• fix getting the correct latitudes-longitudes when the variables "lat" and "lon" are used with the following mapping from x and y:

[codecov-commenter]

Codecov Report

All modified and coverable lines are covered by tests :white_check_mark:

Project coverage is 89.78%. Comparing base (36b2d9c) to head (c25fa7e).

Additional details and impacted files

```diff @@ Coverage Diff @@ ## develop #401 +/- ## ======================================== Coverage 89.78% 89.78% ======================================== Files 120 120 Lines 7653 7658 +5 Branches 675 675 ======================================== + Hits 6871 6876 +5 Misses 651 651 Partials 131 131 ```

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