Add __repr__ and optional description to Collection.
Add CollectionStorage.
Add cpm_selfserve_collection.
PromoteController: update endpoints to accept Collections.
migration: Continue to support targeting "none".
For initial rollout only sponsors can target Collections.
Remove obsolete feedback/ad_inq code
Remove obsolete gold email
Refactor ProfileBar and Account.all_karmas

A couple of minor changes included:
- no longer show the "renew your reddit gold" message if you already
  have an automatically-renewing subscription
- don't show the "friends" button to logged-out users
Improvements to opengraph meta tags
IE: Always use latest rendering engine
Add a convenience method, `quick_time`, for timing with `with`
Rebuild embed buttons for simplicity/speed
Allow get_subreddit_stylesheet_url to be used outside c.site context.

For applying subreddit stylesheets to stuff not in subreddits (like
reddit live!)
Allow media embeds to indicate they don't need <iframe>s.
Add a psuedo-selftext class for live thread embeds.