userffx

Added support for `RUST_LOG`-based module/target level filtering like in [env_logger](https://docs.rs/env_logger/0.10.1/env_logger/index.html#enabling-logging) crate ``` RUST_LOG=warn ./main ``` ``` RUST_LOG=data=debug,hardware=debug ./main ``` ``` RUST_LOG=warn,data=debug,hardware=debug ./main ```