Changeset 2855396

Added ability for admin users to populate empty category images using the image from a category product.
Added ability for admin users to export category products.
Added dimensions to admin product parcel selection.
Changed admin navigation bar to link to catalog and customers sections instead of showing links to subsections.
Changed app structure so that most WordPress submenu items will link to new pages containing only content relevant to that section, rather then loading the entire app.
Changed pagination on most admin index pages so that users can quickly navigate to first and last pages.
Changed selection modal to show cleaner card UI.
Fixed issue with conflicting forms on admin category pages.
Fixed delete action on admin product exports.
Fixed appearance of conditions on admin shipping flat rate page.
Removed non-functioning user interface elements on some selection dialogs.