Expose addSection:atIndex: in header.
Add default cell dequeuing to object table sections.
Add method to support guaranteed table section insertion order.
Fix compiler warning.

By adding code path that will never be reached :/
Add custom footer view feature to parallel header views.
Factor out ATVTableView private header into separate file for reuse.
Refactor ATVTableView#addSection:withIdentifierOrder: into subclass ATVOrderedTableView.