Changed: adapted tests to be system independent

... by not requiring an hardcoded result order
Changed: reindex everything from db between tests

Since DB is recreated between tests, search engine should correspond to
the content as well.
Changed: using integers for STATUS_* constants

 ...to be more in line with the other STATUS_* constants out there as
 well as simplifying the code.
Changed: reducing usage of temporary variables
Added: implementing offset and limit in Solr queries
Added: hardcoded high query limit

... so that search backends behaves identically
Changed: throw an Exception if Solr status != 200
Added: deleteContent() search backend operation
Fixed: correct some fixture data for Solr integration tests
Added: support for some multi valued field in Solr
Added: main location information in Solr
Fixed: sorting on a location property must be on the main one
Added: Passing testsuites to Solr integration tests
Added: priority sort clause and solr index
Added: fixture for Solr test
Merge pull request #230 from patrickallaert/solr-part1

First part of completing integration testing with Solr