Allow datetime search to include start_datetime and end_datetime

[rhysrevans3]

Is your feature request related to a problem? Please describe. If an item's datetime is not set i.e it's using a start_datetime and end_datetime. It's exclude from temporal searches.

Describe the solution you'd like Start_datetime and end_datetime to be included in temporal searches.

Describe alternatives you've considered An advanced datetime search that includes all temporal assets.