Allow to specify a non existing space for creating entries in AWM

It's not possible to select a space where to put entries that does not exist yet when creating or editing an application in AWM: only the existing space are displayed in the picker, and there is no way to specify a reference or to ask for creating a space there. Also being an advanced user doesn't provide a location picker.
This is true when creating the application (when the application space does not exist yet) or when editing the application.