Promote the src/tools crate to the top-level workspace.

The 'src' and 'tests' top-level directories now contain tools sources
and integration tests for any of the library crates.

format-all.sh

@@ -0,0 +1,14 @@
+#!/bin/bash
+
+# Format all sources using rustfmt.
+
+# Exit immediately on errors.
+set -e
+
+cd $(dirname "$0")
+src=$(pwd)
+
+for crate in $(find "$src" -name Cargo.toml); do
+    cd $(dirname "$crate")
+    cargo fmt -- "$@"
+done