Start scraping smilies.
Switch Smilies to queue-based managed object context.
Download image data for smilies.

* A SmileyUpdater can be asked to update image data for all smilies that are missing data.
* A SmileyUpdater can also automatically start downloading data whenever new smilies are added.

Bonus:

* Make a SmileyPrimaryKey type to clarify what's going on when it's being used.