Sortable Table using Polymer Web Components

# Dynamically Changing Columns and Templates

Adding, removing, and reordering `columns` should not break sort.
Changing a `cellTemplate`, and column scoped `headerTemplate`, or `footerTemplate` after load should work correctly.
Column reordering via drag-and-drop should work correctly.

Polymer seems to have broken this in its polyfils - native browsers like Chromium have no issue with changing templates