Ingest data from SSK

SSK features a number of scenarios (currently |27|) relevant for SSHOCMP. They could be mapped to "Activity" or to "Training Material".

The data is available in structured form (TEI) on github

Relevant metadata for mapping is found in the teiHeader. Example: https://github.com/ParthenosWP4/SSK/blob/master/scenarios/SSK_sc_DTABf.xml#L6