Proxy signon reauth to stagecraft

The reauth is happening in stagecraft now but it has to come through the
admin-beta domain.
Add the collectd df plugin

This defaults to collecting inode counts, which is needed for adding an
alert around running out of inodes.
Merge pull request #548 from alphagov/add-collectd-df

Add the collectd df plugin
Remove df from collectd plugin list

Commit cccf932 made use of the df defined type so it has to be removed
from the raw collectd::plugin list.
Merge pull request #549 from alphagov/fix-collectd-df

Remove df from collectd plugin list
Merge pull request #547 from alphagov/proxy-reauth-to-stagecraft

Proxy signon reauth to stagecraft
Add check for low disk inodes

Factor out disk checking into it's own defined type and use that
everywhere.
Merge pull request #550 from alphagov/add-inode-check

Add check for low disk inodes
Add manifest for notifier and add to backend

We need to add some machine setup for the new notifier app. This has
also been setup to run on the hour every hour. The cron_definition var
is just parameters to the cron resource merged with some defautls.
Merge pull request #551 from alphagov/add-notifier-app

Add manifest for notifier and add to backend
Notifier should be in dir that matches repo

Fabric helper functions make assumptions about the name of the directory
based in the name of the repository it is cloning from. We shouldn't
break that contract.
Merge pull request #552 from alphagov/add-notifier-app

Notifier should be in dir that matches repo
Notifier command wants to run in app dir

The command the notifier is likely to want to run in the directory of
the currently deployed version.
Merge pull request #553 from alphagov/add-notifier-app

Notifier command wants to run in app dir