#363 Add placeholder option to input (#370)

* Add placeholder option to input , change type of brightness input to number

 Changes to be committed:
	modified:   examples/lib/defaultHtmlStepUi.js
	modified:   src/modules/Brightness/info.json

* change 0% to 0 in brightness placeholder

examples/lib/defaultHtmlStepUi.js

@@ -71,6 +71,8 @@ function DefaultHtmlStepUi(_sequencer, options) {
             inputDesc.type +
             '" name="' +
             paramName +
+            '" placeholder ="' +
+            (inputDesc.placeholder || "") +
             '">';
         }