This ticket is for the work to move event tracking for article actions from Piwik to event logging.
As elsewhere on iOS, we should track the context (the wiki) and the target of actions. Below the target of actions is marked in  where not obvious.
The actions to track for v1 should be:
- Share (do not currently need to track each share type seperately, just initiation of sharing flow)
- Read [linked page] (another page via a link)
- Read a recommended article [recommended page from the footer]
- Save/unsave a recommended article [recommended page from the footer]
- Text size changed
- Language swtiched [target langauge]
- Table of contents open/close
- Start search on page (as with sharing, no need to wire up the full flow, just initiating it)
- Start edit (edit actions/flow will be tracked elsewhere)
These events are intended to help answer basic usage questions such as:
- How many users change the text size of articles, and do they make multiple adjustments or just "set it and forget it"?
- What percent of users switch languages? What are the most common pairs of languages to switch to/from?
- Do people save articles from this view or only from the Search or Explore View?