Add helper to run a real solr server in embedded tomcat.

The solr-home is the example/solr directory from a solr 4.6.1 zip.
The helper (SolrRunner) downloads the solr.war (to be deployed in tomcat)
the first time it's used into a hidden directory (.solr), to not
pollute git with the solr.war.
Fix typo in ByErrorRateSolrExceptionHandler.
Use deep stubs in httpClient mock to prevent NPE on tearDown/shutdown
Add integration test for FailoverLoadbalancedHttpSolrServer

Removed the exclusion of noggit: this exclusion caused a
  NCDFE: org/noggit/CharArr
when running the integration test.

Integration tests are disabled for test phase, added failsafe plugin
to run them via `mvn verify`.
Merge remote-tracking branch 'upstream/master' into integration-tests
Fix compilation errors after merge from upstream.
Shutdown httpClient in IT as this is no longer done by the FLHSS
Merge pull request #4 from magro/integration-tests

Add integration tests running solr in embedded tomcat