self check and corrections

Add self-checking code that looks to see that overview is populated
and alphabetized. Eventually, this will self-check to see if
methods are collected into subtopics and have reciprocal 'see also'
data.

Standardize phrases so that they don't start with a capital or end
with a period.

Self-check is a work in progress, so it is not yet run by the
bookmaker bots. The self-check should run cleanly, however. To run
it:

./out/skia/bookmaker -b docs -k

The expected output is doc stats. Self-check errors such as missing
methods in the overview would be reported here if there are any.

TBR=caryclark@google.com
Docs-Preview: https://skia.org/?cl=93621
Bug: skia:6898
Change-Id: I8f1f817a7b083b13138ee33d1aa090445e9304c6
Reviewed-on: https://skia-review.googlesource.com/93621
Reviewed-by: Cary Clark <caryclark@skia.org>
Commit-Queue: Cary Clark <caryclark@skia.org>
34 files changed