(WIP) Correct CTR references to UCTR #774
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What we've been calling CTR in the dashboards is actually Unique CTR, UCTR, or user-level CTR. The difference:
CTR: Clicks / Impressions
User-level or Unique CTR (UCTR): Unique Users Who Clicked at least Once / Unique Users Who Saw the Ad
The simplest thing to do first is to correct the labels for what we've got.
This patch fixes the in-tree labels, variables, comments, etc.
Still to do: