add 'defunct' states for shoppingcart (ECOM-737)

add retire method to order class
Rename legacy dash template
Remove Grade Adjustment code from legacy dash
Clean up Grade Downloads section of legacy dash
Clean up Admin section of legacy dashboard
Clean up Forum Admin section of legacy dashboard
Clean up Email section of legacy dashboard
Add CSS rules for legacy dash deprecation warnings
Clean up Manage Groups section on legacy dashboard
Remove deprecated cohorts management on legacy dashboard
Clean up Datadump section on legacy dashboard
Only show "Course Statistics at a Glance" in the Admin tab
LMS: adding in basic is-deprecated visual styling
Style cleanups: legacy instructor dashboard
Merge pull request #6151 from edx/adam/add-defunct-states-for-cart

Adam/add defunct states for cart
Merge pull request #6014 from edx/sarina/legacy-dash-cleanup

Legacy dash cleanup
Make a generic django field for storing OpaqueKey classes
Extract common base functionality for storing xblock fields in the relation db
Move lms.lib.xblock into lms.djangoapps.lms_xblock in preparation add database backed configuration to it
Add a configuration model for managing XBlockAsides