use IPython's configuration system for DrQueue settings

[kaazoo]

Imported from Redmine: http://ipython.org/ipython-doc/dev/config/overview.html

For email configuration, a simple JSON file is used. But settings inside IPython could be better when all data is stored on a shared filesystem.

[jedie]

working links:

https://ipython.org/ipython-doc/2/development/config.html https://ipython.org/ipython-doc/3/development/config.html