DATASOLR-147 - Upgrade to Solr 4.10.1 (requires Java 7)

Source code remains Java 6 compatible though we now required at least Java 7 to run the build. In case running on Java 7/8 is not an option one has to plug in a solrj version prior to 4.8.
DATASOLR-208 - Prefix solr functions.

We now prefix functions at root level with {!func}.
DATASOLR-160 - Add Stats for Field
Prepared issue branch.
DATASOLR-160 - Add Stats for Field
introduced equals and hashcode to SimpleField;
implemented StatsOptions for statistics request;
introduced Stats and SelectiveFacet annotations for field statistics request;
introduced statsOptions to Query;
added statsOptions parsing on DefaultQueryParser;
introduced interpretation of Stats and SelectiveFacet to SolrQueryMethod;
added result conversion for StatsFieldInfo from SolrJ to spring-data-solr model;
added documentation for field stats;