Delete all legacy code and files

legacy/crawler.py

legacy/examples/oai_harvest/example_execution.txt

legacy/examples/oai_harvest/list_records.py

legacy/identifiers/__init__.py

legacy/identifiers/identifiers.py

legacy/mining_goals_and_research_questions.md

legacy/tests/crawler/mined_data_ref/889110/889110.bib

legacy/tests/crawler/mined_data_ref/889110/889110.html

...ts/crawler/mined_data_ref/889110/SARSense_finalreport.pdf

legacy/tests/crawler/test_crawler.py

legacy/tests/miner/mined_data/889110.bib

legacy/tests/miner/mined_data/889110.html

legacy/tests/miner/mined_data/SARSense_finalreport.pdf

legacy/tests/miner/mined_data_ref/889110.bib

legacy/tests/miner/mined_data_ref/889110.html

legacy/tests/miner/mined_data_ref/SARSense_finalreport.pdf

legacy/tests/miner/test_miner.py

tests/legacy/juelichdata_sitemap_df.csv

tests/legacy/msc/msc_example.json

tests/legacy/msc/msc_example_2.json