Cross-Model Index Filtering UI

Provide a UI and underlying support for cross-model filtering. This is particularly important in the People index view.

The following screenshot shows how we might approach this to handle more advanced filtering (as well as showing / hiding columns in the index views):

• Additional models would be contained in their own subset of fields (see how From/Thru dates work now) with default fields shown and with a show/hide fields for filtering drop-down "..."
• The "More" button shown here (language to be determined) would be a dropdown to pick additional models that can be used for filtering. Some would be on by default, e.g. for People, these would be Names, Identifiers, Email Addresses, and Roles.
• The columns show/hide drop-down is independent of the filtering tools - and will (probably) only provide a list of available columns from the model of the current index.