[FEATURE] Configuration option to select specific fields for querying when "search all fields"

[Kxka]

Overview of feature request

What kind of user is the feature intended for?
Systems Administrator

What inspired the request?
"searching all fields" leads to long query times

What existing behavior do you want changed?
Admin should be able to choose which fields to query from when users search using "search all fields" label.

Any brand new behavior do you want to add to Islandora?

Any related open or closed issues to this feature request?