Add dj.config + support methods and remove dj.set

[guzman-raphael]

• Add dj.config user access. Support get, set, and helper methods e.g. load, save, restore, etc.
• Remove dj.set and convert to dj.config.
• Update configuration to match https://github.com/datajoint/datajoint-python/blob/master/datajoint/settings.py such that 1 configuration file may be used between both clients.
• Add configuration for database.port and parse from host if defined.
• Add tests

Fix #186