Added link to stats to access the web version.
Added stats tracking for users who open the web version of stats.
Modified text, removed blue coloring, and added disclosure indicator.
Vertically centering link to web stats.
Adjusting vertical offset to stats web link.
Updating StatsLinkToWebviewCell header's.

I used Xcode Refactoring to rename these files but forgot that it
doesn't update the headers accordingly.
Adjusted StatsLinkToWebviewCell to align with style guide.
Merge pull request #1277 from wordpress-mobile/issues/1223-stats-link-to-web-version

Added link to stats to access the web version.