Updating Solr class

I have changed the Solr Client properties access in order to set this service class able to be extended properly.
With this change a developer could specify his own class as the service class and access the properties by extending it.

When it is needed direct access to the configured Solr Client taking advantage of this bundle it is required.
For example I needed custom query and custom results set which were not supported by the SolrBundle.
Merge pull request #78 from davidvartanian/patch-1

Updating Solr service class