SemanticScholar Importer for creating parquet files

This version introduces major changes with respect to the original release, since now Semantic Scholar papers are imported as parquet tables rather than as a SQL-type database.

Initial release

This is the first fully functional release of the importer for Semantic Scholar. The importer needs SemanticScholar Open Research Corpus and creates a Postgres database with that.

Further work is expected for enriching citations and author information with additional information from other sources.

Initial version

v0.1

Initial commit.