Add cargo tool

Review Request #10337 — Created Nov. 29, 2018 and discarded — Latest diff uploaded

Information

ReviewBot
master

Reviewers

This adds a Review Bot tool for analyzing Rust code using the cargo subcommands
Clippy (for linting Rust code) and rustfmt (for checking code formatting
against style guidelines). The cargo tool includes options for which Clippy
linters to include or exclude.

The cargo tool has been tested manually on a Rust project. The Clippy options
have also been tested.