Add a new property to control dynamic title

[shabbyk]

Currently there is an option to select dynamic title which display the number of selected item like

1 selected

I want to add a property and a bit of code that will keep the default text and display the number of selection beside it inside brackers.

defaultText (number of selection)

So it default text is myOptions and the number of selections is 5 then

myOptions (5)

Note: As this is my first pull request in git I am not sure how to make one. So if this a wrong window or if I have done some mistake please guide me. Thanks! :)