Isofit

Small patches to the v3.0.0 release.

**Technical updates:**

- improvements to LUT netCDF creation performance: now using a writer queue, simulations return values to the original ray call to be saved

**Bugfixes:**

- added sphinx_rtd_theme to environment file to fix broken readthedocs build
- fixed bug in assigning mean elevation to LUT grid

This is the new major ISOFIT 3x release that adds multiple new features, updates, and bug fixes.


**Main features**

- new handling of look-up-tables (LUTs), including the option to provide custom prebuilt LUTs
- centralized radiative transfer physics for more flexible development and experimentation
- test coverage for major functionality
- click command line utilities, including download of external data and example files
- a more flexible isofit.ini file used to discover various paths such as tests, data, and examples
- instructions for dev environment setup and a collection of setup scripts
- numpy implementation of the sRTMnet emulator (removes `tensorflow` dependency)


**Technical updates and bug fixes**

- cleaned up ray initialization to not rely on external calls
- updated authorship files
- wavelength checks to ensure that spectral grids obtained from the surface model or an externally provided wavelength file match the instrument specifics given in the input radiance cube
- support for the GAO instrument
- removal of package dependencies, including `matplotlib` and `gdal`
- removal of outdated docker image
- new test labeling for CLI workflows
- deprecation of `LibRadTran` support

Updates include:

- New physics-based sun+sky glint model for water surfaces
- New feathering of surface model block diagonal prior covariances
- EnMAP support in apply_oe.py
- Instructions for dev environment setup and a collection of setup scripts
- Fix to broken readthedocs build
- Update to release workflow

Updates include:

- Removal of GDAL dependency.
- Fix of `ray` imports in order to safely get the local-only wrapper.
- Patch to the interpolation function making sure that mlg respects degree/radians based interpolation.
- Patch fix to read loc data.

Updates include:

- Deprecated `ndsplines` interpolation due to missing package availability on conda-forge.
- Removal of `protobuf` from package dependencies.
- Installation of `ray`, `xxhash`, and `tensorflow` from conda-forge.
- Upload of package data and examples to the conda-forge release.
- Added `pygrib` requirement in `setup.cfg`.
- Simple check for length of surface elevation grid.

Updates include:

- Support for AVIRIS-3
- New parameterization of surface reflectance in multi-transmittance MODTRAN template file
- Bug fixes