[MobLab] Moblab Setup page.

* Adds a new page located at /moblab_setup
* 2 are on this page: 1 to upload a Boto Key and 1 to edit the config values.
* Link to /moblab_setup is visible only on a moblab system.
* RPC's that execute moblab_setup's actions are gated by a decorator that
  limits them to only run on a moblab_system.
* Unittests for new RPC's.
* Editting the config values, writes the full config to shadow_config.ini and
  reboots the system so changes takes effort.
* Resetting the config values, makes shadow_config.ini an empty file and
  reboots the system so it is restored.
* Uploading the boto key uses shutil.copyfile to write in the new boto file's
  contents to the boto file location.

BUG=chromium:396694
TEST=unittests, Uploaded a boto key and successfully ran a suite, editted
config and ensured changes were written into shadow_config, & reset config
and ensured that the default settings were restored.
DEPLOY=afe,apache
CQ-DEPEND=CL:212322
CQ-DEPEND=CL:212323
CQ-DEPEND=CL:212295

Change-Id: Ie354a2df310393045f3116e93004f58ea671de36
Reviewed-on: https://chromium-review.googlesource.com/209685
Reviewed-by: Simran Basi <sbasi@chromium.org>
Commit-Queue: Simran Basi <sbasi@chromium.org>
Tested-by: Simran Basi <sbasi@chromium.org>
17 files changed