Added some methods to WPMobileStats to help with super/people props.
Adding super properties for some general cases.

- Number of times opened reader
- Number of times opened notifications
- Number of times opened stats
- Number of times opened view admin
Adding super properties for some reader cases.

- Number of reader items opened
- Number of reader items liked
- Number of reader items unlikes
- Number of reader items reflagged
Adding super properties for items shared.

- Number of articles shared
- Number of articles shared via email
- Number of articles shared via Twitter
- Number of articles shared via Facebook
- Number of articles shared by Weibo
- Number of articles sent to Pocket
- Number of articles sent to Instapaper
- Number of articles sent to Google Plus
Adding super properties for notification actions.

- Number of notifications performed action against
- Number of notifications replied to
- Number of notifications opened (detail)
- Number of comments approved through notifications
- Number of comments unapproved through notifications
- Number of comments trashed through notifications
- Number of comments untrashed through notifications
- Number of comments flagged as spam through notifications
- Number of comments unflagged as spam through notifications
- Number of blogs followed through notifications
- Number of blogs unfollowed through notifications
Adding super properties for posting actions.

- Number of posts published
- Number of posts updated
- Number of photos added to posts
- Number of videos added to posts
- Number of featured images assigned to posts
Fixing bug with some methods in WPMobileStats
Added super properties for post details.

- Number of posts with photos
- Number of posts with videos
- Number of posts with categories
- Number of posts with tags
Extracted a few methods out of EditPostViewController.

Moved hasPhoto, hasVideo, hasCategories, and hasTags out of
EditPostViewController and into Post/AbstractPost as the methods were
more query methods that better belonged on the model than the
controller.
Merge pull request #1534 from wordpress-mobile/feature/add-super-properties-for-mixpanel

Adding super properties to mixpanel