Added text labels to moderation buttons.

Clearer moderation icons.
Added ability for WPContentView to display the date in the 'byView'.
Added a vertically stacked UIButton subclass to use for the moderation buttons.
restored `addActionButton` method back to its original state.
Added alert prompt to be shown when a comment couldn't be moderated.
removed now unused methods from `ContentActionButton`
Adjusted button size back to 48 pixels.
Added 'Un' toggle states for the Trash and Spam buttons.
Added action sheet delete prompt for trashing a comment since it is destructive.

Added error alert prompt if moderation fails in `CommentViewController`
Removed now unused icons.
Use correct name for new spam icon.
First pass at following site via URL

Groups site related methods into its own service.
Stubs a FollowedSitesViewController.
Adds check for modal view controller.
Adds ReaderSite model and fleshes out followed sites vc
Wires up followed sites view controller.

Shows sites the user is following.
Supports unfollowing sites from the list.
Adds a no results view.
Merge branch 'develop' of github.com:wordpress-mobile/WordPress-iOS into issues/1976-follow-blog-by-url

Conflicts:
	WordPress/WordPress.xcodeproj/project.pbxproj
Update stats pod to 0.0.5, add timezone support to BlogService
Merge branch 'develop' into issue/2141-stats-0.0.5
Made GMT default time zone for site until blog options are synchronized