* Get rid of unsafe code unless really necessary
* Add lint levels where appropriate
Some crates (air-beautifier, air-testing-framework) have lot of
rust_2018_idioms violations, that will be resolved later.
* Refactor `avm-server` interface mod to new crate (#294)
The new crate name is `avm-interface`.
It allows to build fully native air-trace, including pure WASM build.
* Make fully native air-trace build
Unless `wasm` feature is enabled (default), fully native build is
produced. You may build WASM air-trace binary with
`cargo build --target wasm32-wasi --no-default-features --release -p air-trace`
* Fix tracing output on native air-trace build
Wrong option was used.
