IA Pages - add ability to filter index results by field

@russellholt @jdorweiler @jbarrett 

Now if you click on the status or on one of the topics it takes you to the index, filtering the results in order to just show the IAs which have the same status or topic.

Example screenshot, showing just IAs with the "code & hacking" topic:
![screen shot 2014-11-03 at 19 31 29](https://cloud.githubusercontent.com/assets/3652195/4998597/f44f2752-69d9-11e4-95c6-e59a9bd4f438.png)