bug 842385 - update zamboni-stage configuration for sentry

This is a big configuration change, I've copied the config files from sites/altdev/* over and tried to keep all the staging area's domain settings.  Please review all domain name changes carefully to  make sure I haven't botched anything.

It looks like a *lot* of configuration was out of date, not just metlog, so some thing may be broken here.  You may want to just grab the metlog specific changes and port over the other settings yourself.

- metlog specific changes relevant to bug 842385 are contained in:
  * sites/stage/settings_mkt.py:line 54 to set django-statsd to use
    metlog as transport for statsd
  * sites/stage/settings_mkt.py:line 148-162 to configure the metlog
    client and instantiate it