Add a chapter to the Language Guide for Ownership

[airspeedswift]

This is an early draft of a chapter on Ownership for the Language Guide. So far it only includes noncopyable types, but will later cover non escapable types as well, including a description of Span.

I am slightly torn about the example to use. The file example is already used in the classes chapter. A better example would be the implementation of a Box type using unsafe pointers, but this would be a departure from the rest of the book.

This addition will eventually also need to rework other chapters, including where it's stated that only classes can have deinitializers, and to downscope the coverage of ~ in the protocols chapter slightly, moving some of that content here but keeping a brief description with a forward reference.

• Decide on hyphenation of noncopyable
• Add coverage of Escapable
• Add coverage of Span
• Rework Deinitializers chapter
• Rework Protocols chapter