Revisit ContentExtractor (renamed from PopupInteractor)

/**
* An interface for wrapping extracting data from features. The PopupManager
* relies on a Context object. Application logic in the MapPresenter needs a PopupManager but
* should have no knowledge of Android specific objects (like Context), so this interface
* is used to interact with the PopupManager.
*
* TODO Question for Dan, thoughts on this design?
* See this link for more:
* http://stackoverflow.com/questions/34303510/does-the-presenter-having-knowledge-of-the-activity-context-a-bad-idea-in-the/34664466#34664466
*/

Comment from Dan:
```I agree that Android Context needs to be removed from PopupInteractor. Furthermore, in the current implementation, we should consider renaming the Popup* named classes to something closer to Callout as those are the contents we are returning to the View.```