Change socioeconomic status class in BCIO

[paulinaschenk]

• Change label of "socioeconomic status" to "socioeconomic position"
• Update definition from "A personal attribute reflecting a person's economic and social position in relation to others, based on their income, education, or occupation." to be more general, removing ‘based on their income, education, or occupation’ and add them as examples.

These suggested changes are also being communicated with the lead of the Population Ontology.