[enh] #68 add Data Access Layer crate

dal/Cargo.toml

dal/block.rs

dal/constants.rs

dal/dal_event.rs

dal/dal_requests.rs

dal/endpoint.rs

dal/identity.rs

dal/lib.rs

dal/parsers/blocks.rs

dal/parsers/certifications.rs

dal/parsers/excluded.rs

dal/parsers/identities.rs

dal/parsers/memberships.rs

dal/parsers/mod.rs

dal/parsers/revoked.rs

dal/parsers/transactions.rs

dal/test.db

dal/tools.rs

dal/writers/block.rs

dal/writers/certification.rs