Remove Google Checkout.

The service is being discontinued.
Revert "Promo admin tool"

This reverts commit 301512551aca1231f7bc3cbd7bca96720415ef35.
Stop using Promote_Graph in Promotion_Summary.
Delete Promote_Graph.
PromotionWeights.get_campaigns can filter by sr_name.
inventory: get_campaigns_by_date method.
inventory: split out get_predicted_pageviews.
PromoteInventory page.
Better handling of ignore in inventory methods.
Move inventory multiplier to INVENTORY_FACTOR constant.
Delete unused promote.traffic_totals.
PromotionWeights: delete get_schedule and bid_history.
Promotion_Summary: subtract refund_amount.
Promotion_Summary: comment explaining campaign accounting.
Count clicks on the "comments" link for a selftext promoted link.
sgm: use the time parameter.
Add timer around normalized_hot.
set_subreddit: Protect against IDNA encoding errors.
Use sgm to cache each subreddit's normalized_hot links.
find_preview_comments/links: use sr rather than c.site.