rename disabled to enabled (#2750)

lib/android/app/src/main/java/com/reactnativenavigation/parse/Button.java

 public class Button {
 	public String id;
 	public Text title;
-	public Bool disabled;
+	public Bool enabled;
 	public Bool disableIconTint;
 	public int showAsAction;
 	@ColorInt public int buttonColor;
 		Button button = new Button();
 		button.id = json.optString("id");
 		button.title = TextParser.parse(json, "title");
-		button.disabled = BoolParser.parse(json,"disabled");
+		button.enabled = BoolParser.parse(json,"enabled");
 		button.disableIconTint = BoolParser.parse(json,"disableIconTint");
 		button.showAsAction = parseShowAsAction(json);
 		button.buttonColor = json.optInt("buttonColor", NO_INT_VALUE);

lib/android/app/src/main/java/com/reactnativenavigation/views/TitleBarButton.java

 	void addToMenu(Context context, final Menu menu) {
 		MenuItem menuItem = menu.add(button.title.get(""));
 		menuItem.setShowAsAction(button.showAsAction);
-		menuItem.setEnabled(button.disabled.isFalseOrUndefined());
+		menuItem.setEnabled(button.enabled.isTrueOrUndefined());
 		menuItem.setOnMenuItemClickListener(this);
 
 		if (hasIcon()) {
 	}
 
 	private void setIconColor() {
-		if (button.disabled.isFalseOrUndefined()) {
+		if (button.enabled.isTrueOrUndefined()) {
 			UiUtils.tintDrawable(icon, button.buttonColor);
 			return;
 		}
-
 		if (button.disableIconTint.isTrue()) {
 			UiUtils.tintDrawable(icon, button.buttonColor);
 		} else {