Consolidates comment models in core data schema.
Consolidate properties and methods in Comment class.
Remove references to ReaderComment class

Comments out code related to syncing and displaying ReaderComments from the ReaderPostDetailViewController.
Commented code will be deleted as the refactor progresses.
Add missing header import.
Silence a warning and crash due to work in progress.
Add hierarchy to the comment model.
Updates remote comment and remote rest service.

Adds support for author's avatar url and syncing a hierarchical list of comments.
Adds service methods for syncing hierarchical comments
Model mapping for the comment changes.
Return count upon a successful sync.
Basic infinite scroll behavior.

Removes some dead or obsolete code.
removes text from back button text
Remove obsolete/unnecessary methods from ReaderPost model.
Removes obsolete methods. Organizes method groupings.
Reader detail uses sync and table view helper classes.

Basic implementation. Some features, like load more spinner and section header, not yet implemented / restored.
Merge branch 'develop' of github.com:wordpress-mobile/WordPress-iOS into issues/46-comments-refresh

Conflicts:
	WordPress/Classes/Networking/CommentServiceRemoteREST.h
	WordPress/Classes/Networking/CommentServiceRemoteREST.m
	WordPress/Classes/Services/CommentService.h
	WordPress/Classes/Services/CommentService.m
	WordPress/Classes/WordPress.xcdatamodeld/WordPress 21.xcdatamodel/contents
	WordPress/WordPress.xcodeproj/project.pbxproj
Prevents hitting callback when the instance was released
reverts fix in 9c0ebb9
removes title from back button on presenting VC
Changes from feedback. Adds a sync helper.