Support --message-format=json option

[dtretyakov]

In the cargo 1.12 we can use --message-format=json option to get messages in the json format: https://github.com/rust-lang/cargo/pull/3000

It affects bench, build, doc, run, rustc, rustdoc, test.

Docs: https://github.com/rust-lang/cargo/blob/master/src/doc/machine-readable-output.md