Add metrics and venv to wmatrix DB update pipeline

As part of this addition, refactor update_rawdb and update_wmdb to pull
 shared code into a new lib file. All logging will occur from a single
 line.
In order to enable local checks and use of chromite, also add virtualenv for
 dependencies.

BUG=chromium:756606
TEST=Run live.

Change-Id: I45de3285be35b34b0f3b23f22afc561a263249b0
Reviewed-on: https://chromium-review.googlesource.com/707825
Commit-Ready: Jacob Kopczynski <jkop@chromium.org>
Tested-by: Jacob Kopczynski <jkop@chromium.org>
Reviewed-by: Jacob Kopczynski <jkop@chromium.org>
12 files changed