educationalContext: English prefLabels and altLabels should follow a common style

[Criamos]

While working on fobizz_spider, I noticed that we need a mapping for their educationalContext-values, but our English prefLabel and altLabel values aren't following the same style: Some values are capitalized, others are written in lower-case.

This makes mapping more cumbersome because instead of being able to call .lower() or .capitalize() on the to be mapped Python strings, I need to check how each value is saved in the educationalContext-Vocab.

The list of values that Fobizz uses for their educationalContext can be found here by selecting the "Klassenstufen"-Filter.

MAPPING_EDUCATIONALCONTEXT = {
        "Elementary School": "elementary school",  # Grundschule
        "Lower Grade": "Secondary I",  # Unterstufe? Kl. 5-7 (untere Hälfte der Sekundarstufe I)
        "Middle Level": "Secondary I",  # Mittelstufe? Kl. 7-9 (obere Hälfte der Sekundarstufe I)
        "Upper School": "Secondary II",  # Oberstufe?
        "Vocational School": "vocational school",
        "Special School": "special education",
    }

If you take a look at the educationalContext.ttl, you'll notice edge-cases like Further Education immediately followed by continuing education.

My proposal would be: All English prefLabeland altLabel values should be lowercase. This would solve the problem of suddenly facing unexpected capitalized letters (which would throw off our automatic mapping).