FIX Fixes #965. Allow user date-settings to show on GridField Page admin

- Relies on framework PR #2961.
Merge pull request #968 from phptek/issue/965

FIX Fixes #965. Allow user date-settings to show on GridField Page admin
API Filter by date created for files
Added test cases
Do not merge before https://github.com/silverstripe-labs/silverstripe-behat-extension/pull/32

ref: CWPBUG-144