Small Features to csvimport

Hey,

I added a couple features to the csv import. I added django signals to the app, to allow the model to custom format a row. So if its some row that the app cant figure out we can transform it if we know what it is. 

I also added appconf to allow the app to be more customizable. Right now I am just using it to manually select which models I am allowing to import from a CSV. But can be used for other settings. 

There is some minor clean up I did. Sorry. Hopefully I didnt hurt blame to much.