DATASOLR-83 - Add support for Realtime GET

Introduction of getById to SolrOperations;
Documentation for real-time get.

Original Pull Request: #45
DATASOLR-83 - Add support for Realtime GET

Use SolrRequest implementation for executing real time get request.
Added issue number to tests.
Added since tag to new methods.
Rebased on new master.
DATASOLR-83 - Add support for Realtime GET.

Introduced some tests for SolrRealtimeGetRequest.
DATASOLR-196 - Introduce connect() and notOperator() to Criteria.

connect() allows to explicitly create bracketing.
  //z:roo AND (x:foo OR y:bar)
  where(“z”).is(“roo”).connect().and(where(“x”).is(“foo”).or(“y”).is(“bar”))

notOpereator allows to wrap whole or expression parts inside a negating statement
  //z:roo OR -(x:foo OR y:bar)
  where("z").is("roo").connect().or(where("x").is("foo").or("y").is("bar").notOperator())
DATASOLR-205 - Create Documentation for Pivot Faceting
documented use of pivot faceting.
DATASOLR-209 - GroupOptions Interface Polishment
renamed field groupCount to totalCount;
renamed getGroupRows to getLimit;
removed Group prefix from methods with exception of groupBy*, groupMain
and groupFacet;
introduced validation of rows and cachePercent parameters.
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.

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.

Original Pull Request: #46
DATASOLR-160 - Polishing.

Added issue numbers and author information.
Moved and renamed tests.
DATASOLR-214 - Fix test leaving index files behind.

We new explicitly remove the data directory using a shutdown hook.
DATASOLR-216 - Use PersistentPropertyAccessor API via PersistentEntity instead of BeanWrapper.

Prefer ConvertingPropertyAccessor over BeanWrapper for retrieving/setting values on target instances.
Relates to DATACMNS-596.