Add constants for built-in Shuffleboard widgets and layouts (#1468)

Prevents users from having to remember (and correctly type) the names of Shuffleboard widgets.

wpilibc/src/main/native/include/frc/shuffleboard/ShuffleboardWidget.h

@@ -10,6 +10,7 @@
 #include <wpi/Twine.h>
 
 #include "frc/shuffleboard/ShuffleboardComponent.h"
+#include "frc/shuffleboard/WidgetType.h"
 
 namespace frc {
 
@@ -36,6 +37,22 @@ class ShuffleboardWidget
    *
    * @param widgetType the type of the widget used to display the data
    * @return this widget object
+   * @see BuiltInWidgets
+   */
+  Derived& withWidget(const WidgetType& widgetType) {
+    return WithWidget(widgetType.GetWidgetName());
+  }
+
+  /**
+   * Sets the type of widget used to display the data. If not set, the default
+   * widget type will be used. This method should only be used to use a widget
+   * that does not come built into Shuffleboard (i.e. one that comes with a
+   * custom or thrid-party plugin). To use a widget that is built into
+   * Shuffleboard, use {@link #withWidget(WidgetType)} and {@link
+   * BuiltInWidgets}.
+   *
+   * @param widgetType the type of the widget used to display the data
+   * @return this widget object
    */
   Derived& WithWidget(const wpi::Twine& widgetType) {
     this->SetType(widgetType);