Added binding convert option.

ui/core/bindable.d.ts

@@ -17,6 +17,27 @@
          * True to establish a two-way binding, false otherwise. A two-way binding will synchronize both the source and the target property values regardless of which one initiated the change.
          */
         twoWay?: boolean;
+        /**
+         * An expression used for calculations (convertions) based on the value of the property.
+         */
+        expression?: string;
+    }
+
+    /**
+     * An interface which defines methods need to create binding value converter.
+     */
+    export interface ValueConverter {
+        /**
+         * A method that will be executed when a value (of the binding property) should be converted to the observable model.
+         * For example: user types in a text field, but our business logic requires to store data in a different manner (e.g. in lower case).
+         * @param params - An array of parameters where first element is the value of the property and next elements are parameters send to converter.
+         */
+        toModel: (...params: any[]) => any;
+        /**
+         * A method that will be executed when a value should be converted to the UI view. For example we have a date object which should be displayed to the end user in a specific date format.
+         * @param params - An array of parameters where first element is the value of the property and next elements are parameters send to converter.
+         */
+        toView: (...params: any[]) => any;
     }
 
     /**
@@ -45,6 +66,7 @@
         unbind(property: string);
 
         //@private
+        static _getBindingOptions(name: string, bindingExpression: string): BindingOptions;
         _updateTwoWayBinding(propertyName: string, value: any);
         _onBindingContextChanged(oldValue: any, newValue: any);
         //@endprivate