Add documentation properties to SKOS

[acka47]

From https://github.com/hbz/skohub-ssg/issues/1#issuecomment-493882836:

Going forward with the vocab, we might add some documentation properties (scopeNote etc.) with content from the description pages under https://www.hochschulkompass.de/studienbereiche-kennenlernen.html, e.g. https://www.hochschulkompass.de/kunst-musik-und-design.html for F146. EDIT: We should of course also add a name and description of the vocab as a whole.

[acka47]

I added skos:definition and – where applicable – skos:scopeNote to all top-level concets (except one wher eno information could be found) and to three second-level concepts (which means that 79 second-level concepts are still without documentation properties). Please note:

• I used markdown syntax for the literals.
• As some strings contained new lines I used triple quotes for the strings (see https://www.w3.org/TR/turtle/#turtle-literals where it says that singles quotes don't allow new lines).

See for example:

https://github.com/hbz/skohub-ssg/blob/cc50cd4379146acb9ccdf39297e317bc2fd77783/test/data/systematik.ttl#L29-L32