Misc tweaks

Hi Lasindu,

I have a couple of improvements to your last pull adding the image slider module.

- Use JHtml to initialise JavaScript, this will ensure that the necessary JavaScript dependencies (Bootstrap and jQuery) are loaded as well
- Modify JHtmlBootstrap::carousel() to allow the selector param to specify class or id (this was previously hard coded to only work with a class selector and wouldn't work with your use of an id)
- Missing closing </div>