Optional "native like" panel indicator functionality.

I've added the option to have a "panel indicator" which slides in proportion to the sidebar as it does in native Android applications using the Holo style interface.
This can be utilised by passing the ID of the element containing the indicator.

![screenshot_2014-02-25-16-03-03](https://f.cloud.github.com/assets/1125046/2259605/090d4544-9e37-11e3-9886-a5ef891fa908.png)
![screenshot_2014-02-25-16-03-09](https://f.cloud.github.com/assets/1125046/2259607/0c98a87a-9e37-11e3-97d4-40da0752850f.png)