Sortable columns in index views

Added three new date columns to resource index views. Created date is the date that the resource was created. Modified refers to the date that the resource’s configuration was last modified (e.g. a trait was added to a cohort’s definition). Lastly, processed is the last time the output was processed by Faraday (i.e. the output changed). Additionally, columns can now be sorted by ascending or descending values.