implement "Import spectral library from JSON file" algorithm

[Andreas Janz]

We can already export libraries to a human-readable JSON file:

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Now we need the corresponding import algorithm.

[Andreas Janz]

We now use GeoJSON format, which can be created with QGIS API. To make it fully human-readable, we will replace the binary profile fields with text fields:

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[Andreas Janz]

@Benjamin Jakimow FYI:
For now, GeoJSON is concidered an external SpectralLibrary format, because the EnMAP-Box isn’t yet supporting text fields as profiles.
To import it into the internal format, you can use the “Import spectral library from JSON file“ algorithm.

[Andreas Janz]

@Benjamin Jakimow already implemented support for human-readable JSON/Text-Fields for Profiles. So we don’t need this algorithm anymore.