added about page

see #1993 and #2158

**Questions:**
* is there a function/variable to get the admin email?
* should the /help index action redirect to the about index action?
* any more output on about page?

New Features:
* Add about to dashboard navigation
* Add about to sidebar on bottom
* Add about to main navigation
* Moved help-OL to partial.
* Included help-OL-partial in about page

About & Help icon in top navigation:
![Bildschirmfoto vom 2012-12-08 11:15:45.png](https://f.cloud.github.com/assets/327488/1705/85bcfeec-4120-11e2-8c90-f17c36600706.png)

About & Help in sidebar navigation on dashboard
![Bildschirmfoto vom 2012-12-08 11:15:51.png](https://f.cloud.github.com/assets/327488/1706/8dfaed44-4120-11e2-8f29-0b6ef44f6434.png)

About page with help-ol partial
![Bildschirmfoto vom 2012-12-08 11:16:20.png](https://f.cloud.github.com/assets/327488/1707/90278f8c-4120-11e2-8cf4-416113f1e3e1.png)