Solr search now works!

Tested with Solr 4.2.1 on OSX.
Basic faceted search now working
Use minimum price for group products in price facet
Price range faceting now works
Use setting to confiture facets

This supports range facets specified by "facet queries".
Updated makefile for building Solr indexes
We now require purl>=0.6

As it add some super-handy method for manipulating URLs that uses lists
of query params.  These are used for manipulating Solr URLs.
Add handling of when Solr is down