swh-indexer: Bootstrap db model

.gitignore

sql/Makefile

sql/bin/db-upgrade

sql/bin/dot_add_content

sql/doc/json

sql/doc/sql

sql/json/.gitignore

sql/json/Makefile

...json/indexer_configuration.tool_configuration.schema.json

sql/json/revision_metadata.translated_metadata.json

sql/swh-data.sql

sql/swh-enums.sql

sql/swh-func.sql

sql/swh-indexes.sql

sql/swh-init.sql

sql/swh-schema.sql

sql/upgrades/114.sql