Improve load testing tool.

Rewrote/reworked mwalker's `injectMetabooks` script into a more complete
load-testing tool.  This can also be used to quanify failures and find
regressions.

The list of page titles and prefixes in `pages.list` comes from the
Parsoid round-trip testing tool.  It consists of about 10k randomly
selected articles from a number of large wikis.

Change-Id: I8cfe705e366b71606ebd7f5a81c7796d5153145c
Load testing tool: Don't report deleted articles as failures.

Change-Id: Ide449fac5f160eefb08def56dca949e279975790
Updating to latest masters

Deployed new service (34dce8513b9ce0f6c84b22f854f3d732c36c779e):
* Clean up directory size computation, eliminate a spurious log message.
* Add force_render option to help page.

Deployed new bundler (90d0700afb5937ec9ec5bf43f37b653dd1559828):
* Improve Metabook.fromArticles so that it can be used from load testing tool.
* Handle redirects from subpages
  (for example, [[:en:Children's_Heritage/D_O_A]]).

Deployed new latexer (86c1e14305b5109acd68a6bbd3b129692563c195):
* Don't crash if PNG has bogus resolution information
  (for example, [[File:Frederick-II-of-Prussia-Coloured-drawing.png]]).
* Support inline images (like in [[:en:⠦]]).

Change-Id: I0ea573635da22781deb330e922811209f16b5063
Merge branch 'master' into wmf-deploy

Change-Id: If50e5a923324998edbfc392eecac91d6bea3a518