New feature: navigation position

I fixed some things:
- shadow sometimes not showing up
- MonoTouch.Dialog reference was wrong

and I added a new feature:
- possiblity to specify the navigation position (left or right side)
![screen shot 2013-12-18 at 7 16 03 pm](https://f.cloud.github.com/assets/610551/1776035/879c8a30-6810-11e3-937d-0a2af8bf140c.png)
![screen shot 2013-12-18 at 7 16 48 pm](https://f.cloud.github.com/assets/610551/1776036/9377c004-6810-11e3-9beb-7d5745aae5aa.png)

Best,
Chrigu