CHANGE add start date and end date

Really requires a change window I.e. a wide proposed range of dates when the change could take place (giving higher chance of avoiding change freeze or delays in ticket processing etc i.e a window within which the change can be scheduled. These start/end dates should be defined while in New stays and certainly before leaving the Evaluation status.

But also requires a scheduled start and finish date/time, which should be defined when in the Accepted status. This should really be the Schedule status and is completed when the actual change work is scheduled. 

The ticket should be moved into the Pending (or Implement status at the scheduled start date/time.