Added the ability to enable the "AppOffline" rule

I was getting "#ERROR_FILE_IN_USE" issues when deploying. E.g.

![error](https://cloud.githubusercontent.com/assets/1551204/4538261/715cccd6-4dec-11e4-879b-346733ca262b.PNG)

So I updated the script and parameters to include a checkbox which turns on or off the AppOffline rule. [See here for more details](http://www.iis.net/learn/publish/deploying-application-packages/taking-an-application-offline-before-publishing)

![addition](https://cloud.githubusercontent.com/assets/1551204/4538275/a51850a4-4dec-11e4-9dea-937d065dd591.PNG)

Tested and works as expected.