First work on abstraction layers for MongoDB/GridFS and ElasticSearch
usage, making the code easier on the eye and less complex to unit test.
* Introduce init_once() method for all plugins/modules.
* Use global mongo & elastic instance so only one connection is
required, instead of a connection per processed analysis.
* Configuration migration for MongoDB user authentication.
* Proper configuration support for ElasticSearch's multiple hosts.
* Get rid of "settings.MONGO" & "settings.ELASTIC" usage.
* Include elasticsearch==2.2.0 dependency (to be upgraded by #1196).
* Some unit tests to back up the above, but not full coverage.
* Code cleanup & Screenshots unit test fix.
Note that as per their documentation, both the MongoDB and ElasticSearch
Python API's are thread-safe. Other than that, let's hope the untested
changes are fine :-)
Jurriaan Bremer