Change all "IsSupplementedBy" to "IsSupplementTo" (or lower case versions)

Previous versions of the OpenAIRE graph and the ScholeXplorer API returned directed relationships ("IsSupplementedBy" vs "IsSupplementTo" (or lower case versions of this)).

Due to the latest updates of relations in the OpenAIRE graph we should update our source code to align with their simpler, direction-agnostic terminology and remove all inverse translations for now.

In the JSON records returned by the ScholeXplorer API, all types of "closely associated" relation types will be stored in the database as

"Name":"IsSupplementTo"

"SubType":"issupplementto"

and shall be selected as such in the SQL-queries.