Change DataInput selector to use existing chooser model

Make datainput selector dialog use ChooserModelBase (reference: image and texture choosers) and use similar QML, so that datainput selector follows the same popup model as other chooser dialogs.

Other changes to datainput choosed dialog:

First item in the list is always [None] (was: [No control]). Selecting this disables datainput control.

Second item is [Create New], if the available datainput list is empty. Otherwise, second and following items list the available datainputs. [Create New] choice closes the datainput dialog and opens datainput definition dialog (otherwise available from Edit->Data Inputs...)