TicketQuery: add the ''Created'' and ''Modified'' entries to the list of selectable columns.
TicketQuery: add the ''Created'' and ''Modified'' entries to the list of selectable columns.

Closes #4966 (''last modified'' column) and #5326 (''days open'' column).
pkdevbox/trac,pkdevbox/trac,pkdevbox/trac,pkdevbox/trac