#967 rework container model structure

- now FormFieldModel provides information about columns and child fields
- greatly simplified models
- visibility engine fixes

ng2-components/ng2-activiti-form/src/components/widgets/widget.component.ts

@@ -81,6 +81,7 @@ export class WidgetComponent implements AfterViewInit {
 
     /** @deprecated use onFieldChanged instead */
     checkVisibility(field: FormFieldModel) {
+        console.log('checkVisibility is deprecated, use onFieldChanged instead');
         this.fieldChanged.emit(field);
     }