Comprehensive Rust v2 (#1073)

I've taken some work by @fw-immunant and others on the new organization
of the course and condensed it into a form amenable to a text editor and
some computational analysis. You can see the inputs in `course.py` but
the interesting bits are the output: `outline.md` and `slides.md`.

The idea is to break the course into more, smaller segments with
exercises at the ends and breaks in between. So `outline.md` lists the
segments, their duration, and sums those durations up per-day. It shows
we're about an hour too long right now! There are more details of the
segments in `slides.md`, or you can see mostly the same stuff in
`course.py`.

This now contains all of the content from the v1 course, ensuring both
that we've covered everything and that we'll have somewhere to redirect
every page.

Fixes #1082.
Fixes #1465.

---------

Co-authored-by: Nicole LeGare <dlegare.1001@gmail.com>
Co-authored-by: Martin Geisler <mgeisler@google.com>

src/std-types/docs.md

@@ -0,0 +1,45 @@
+---
+minutes: 5
+---
+
+# Language Docs
+
+Rust comes with extensive documentation of the language and the standard library.
+
+For example:
+ * All of the details about [loops](https://doc.rust-lang.org/stable/reference/expressions/loop-expr.html).
+ * Primitive types like [`u8`](https://doc.rust-lang.org/stable/std/primitive.u8.html).
+ * Standard-library items like [`Option`](https://doc.rust-lang.org/stable/std/option/enum.Option.html) or [`BinaryHeap`](https://doc.rust-lang.org/stable/std/collections/struct.BinaryHeap.html).
+
+In fact, you can document your own code:
+
+```rust,editable
+/// Determine whether the first argument is divisible by the second argument.
+///
+/// If the second argument is zero, the result is false.
+fn is_divisible_by(lhs: u32, rhs: u32) -> bool {
+    if rhs == 0 {
+        return false;
+    }
+    lhs % rhs == 0
+}
+```
+
+The contents are treated as Markdown. All published Rust library crates are
+automatically documented at [`docs.rs`](https://docs.rs) using the
+[rustdoc](https://doc.rust-lang.org/rustdoc/what-is-rustdoc.html) tool. It is
+idiomatic to document all public items in an API using this pattern.
+
+To document an item from inside the item (such as inside a module), use `//!`
+or `/*! .. */`, called "inner doc comments":
+
+```rust,editable
+//! This module contains functionality relating to divisibility of integers.
+```
+
+<details>
+
+* Show students the generated docs for the `rand` crate at
+  [`docs.rs/rand`](https://docs.rs/rand).
+
+</details>