[WIP] RUST: Implementing the safe interface over the unsafe C types and functions

src/rust/liblektor-rs/Cargo.toml

src/rust/liblektor-rs/lektor_c_compat/Cargo.toml

src/rust/liblektor-rs/lektor_c_compat/src/c_types.rs

src/rust/liblektor-rs/lektor_c_compat/src/lib.rs

src/rust/liblektor-rs/lektor_c_compat/src/rs_types.rs

src/rust/liblektor-rs/lektor_db/diesel.toml

...-rs/lektor_db/migrations/2022-09-30-204512_initial/up.sql

src/rust/liblektor-rs/lektor_db/src/database/schema.rs