Object containing the view model data of the placeholders:
placeholderName [Type: string] - the name of the placeholder.
placeholderTitle: [Type: string] - the title of the placeholder to display as the container of the placeholder data.
placeholderType: [Type: knockout.observable] - the type of the placeholder
measureSelection: [Type: knockout.observable] - the selected measure of the placeholder
hierarchySelection: [Type: knockout.observable] - The selected hierarchy of the placeholder
measures: [Type: knockout.observableArray] - the available measures of the placeholder
hierarchies: [Type: knockout.observableArray] - the available hierarchies of the placeholder.