[database] Implement v2 support

beat/backend/python/database.py

beat/backend/python/exceptions.py

beat/backend/python/test/prefix/databases/integers_db/2.json

beat/backend/python/test/prefix/databases/integers_db/2.py

...est/prefix/protocoltemplates/different_frequencies/1.json

...ackend/python/test/prefix/protocoltemplates/double/1.json

...kend/python/test/prefix/protocoltemplates/labelled/1.json

...ackend/python/test/prefix/protocoltemplates/triple/1.json

...kend/python/test/prefix/protocoltemplates/two_sets/1.json

beat/backend/python/test/test_database.py

beat/backend/python/test/test_database_view.py

beat/backend/python/test/test_databases_index.py

beat/backend/python/test/test_databases_provider.py

beat/backend/python/test/test_dbexecutor.py