Added all the image urls we got from Bing into Solr/Dropwizard.

*Changed schema.xml and data-config.xml to add the new field into Solr
*Changed solrconfig.xml to make /simpleweighted return the ImgUrl field as well
*Changes to SolrProductEntry, productsearch.xsd, and each resource to capture the Solr changes in Dropwizard.
*Editted the README so that imgUrl appears as a returned field