There are two ways to characterize what I'd like to do. 1) use the EmbeddedSolrServer to launch Solr, and subsequently enable the HTTP GET/json servlet. I can provide the 'servlet' wiring, I just need to be able to hand an HttpServletRequest to something and retrieve in return the same json that would come back from the usual Solr servlet.
2) Use the usual Solr servlet apparatus, but defer its startup until other code in the webapp makes up its mind about configuration and calls System.setProperty to locate the solr home and data directories.
