added edit links for admin inline forms

Hi,

since nested inlines are not available I made a little workaround for this. Inline forms that are associated with an existing model instance have now a little "edit" link that leads to it's admin page.

![edit_link_stacked](https://f.cloud.github.com/assets/1387322/1797665/4c24eb68-6aff-11e3-8508-b1f8adc54b4b.png)

![edit_link_tabular](https://f.cloud.github.com/assets/1387322/1797666/5706e1d0-6aff-11e3-97ee-e01775098981.png)

How to setup:

Just add suit_edit_link = _True_ to the properties of the inline admin class.