Generate bookmaker indices

First cut at splitting bookmaker documentation into reference
and overview. Reference starts with a hyperlinked index,
generated from a public include.

This moves towards typing once, minimizing the information
duplicated in the .h file and the .bmh file.

TBR=caryclark@google.com
Docs-Preview: https://skia.org/?cl=154630
Change-Id: I836622db9b1786bd28c0bce2536cd3caef6e5a32
Reviewed-on: https://skia-review.googlesource.com/c/154630
Commit-Queue: Cary Clark <caryclark@skia.org>
Auto-Submit: Cary Clark <caryclark@skia.org>
Reviewed-by: Cary Clark <caryclark@skia.org>
67 files changed