Support for new service class name for Search API RC4 

This is the work needed for the Pantheon Apachesolr module to support the RC4 version of Search API module on Pantheon. Basically, this patch provides a custom service and connection class used by Search API module and uses a hidden variable Search API module to get it all rolling.

This code assumes the patch in http://drupal.org/node/1407282#comment-7388404 and will not work without it.