Add a search function to Whitehouse petitions and a prominent link to whitehouse.gov.

Many petitions cover the same very important topics, and a search function will allow users to find out if there is already a petition covering the topics they are most interested in. Adding this function will help to ensure that peoples' opinions are not diluted by having to scroll through all available petitions to find the one(s) they want to sign.
The petitions page will be easier to find if there is a prominent link on whitehouse.gov, increasing the awareness of the petition system.