This commit introduces finished working prototype of mentat-storage.py real-time message processing module including appropriate unit tests and basic documentation work. Key features are possible customization of target database and collection, usage of core database configuration file, which can be overriden with local config file, or command line options. Messages are currently stored in database one by one, however batch processing will possibly be implemented in the future.

(Redmine issues: #3364, #1017 and #3361)