reformat parser for IGC and add tests

backend/metagenedb/api/catalog/views/__init__.py

backend/metagenedb/apps/catalog/admin/__init__.py

backend/metagenedb/apps/catalog/models/__init__.py

backend/metagenedb/apps/catalog/serializers/__init__.py

backend/metagenedb/common/utils/parsers/__init__.py

backend/metagenedb/common/utils/parsers/igc.py

backend/metagenedb/common/utils/parsers/kegg.py

backend/metagenedb/common/utils/parsers/ncbi_taxonomy.py

backend/metagenedb/common/utils/parsers/test_igc.py

backend/metagenedb/common/utils/parsers/test_kegg.py

...end/metagenedb/common/utils/parsers/test_ncbi_taxonomy.py

backend/scripts/populate_db/import_igc_data.py

backend/scripts/populate_db/test_import_igc_data.py