Add new Bookmaker bot that runs nightly

The new bot:
1) Extracts all fiddles out of markdown files.
2) Forces fiddle.skia.org to compile all those fiddles and get output in JSON.
3) Scans the output and reports any compiletime/runtime errors.
4) Updates markdown in site/user/api/ using the new hashes (if any) from fiddle.skia.org.

To ensure the bot does not check in unexpected changes:
* upload_md.py makes sure that all modified files are under site/user/api/. It errors out if this is not the case.
* CLs with docs only changes normally have 'NoTry: true' added to their descriptions. This is not done for the new bot because we want to run it through trybots to make sure nothing unexpected snuck in.
* rmistry@ and caryclark@ are automatically CC'ed on all uploaded changes. I plan to watch the bot closely for at least a couple of weeks.


Bug: skia:7310
Change-Id: I759fc8bae1e32a6f175e3b1a895947d14ca5fe3a
Reviewed-on: https://skia-review.googlesource.com/79941
Commit-Queue: Ravi Mistry <rmistry@google.com>
Reviewed-by: Eric Boren <borenet@google.com>
68 files changed