Exploratory development for https://github.com/FriendsOfSymfony/FOSElasticaBundle/issues/410
Don't need postRemove.
Refactor to a single Listener class.  Update tests.
Re-add renamed Listener.
pre/postFlush configuration. Update documentation.
Remove upgrade doc.  Merk will add manually.
Remove debug.
Use constants of corresponding events classes rather than making assumption about string values.
Use bulk insert.  Still working on bulk update/delete which is not yet suppored in Elastica.
Merge remote-tracking branch 'upstream/master'
Bulk update.  Still working on bulk delete for indexes and types in Elastica.
Bulk delete
Merge remote-tracking branch 'upstream/master'
Update tests
Add support for using aliases to allow hot swapping of indexes when populating
Make real index name use uniqid so can be reset within a second
Fixes #459
ElasticaLogger cleanup
Rework configuration validation to fix #461
Merge pull request #493 from tgallice/url_parameter_fix

Rework configuration validation to fix #461