Issue 1767

Database was overkill to store server preferences, config files sounded more natural. So moved from '.js' file to '.json' file, and used nconf. 

Fetching controller reads '.json' file and updates it and raises appropriate event. Botmaster listens to these events (as before), and enables/disables itself.

On startup, botmaster reads '.json' file and enables/disables itself.

All tests are passing. Ran the server, it is able to keep the fetching status across restarts, and it should not hang anymore on fetching status call.
Indent seems off here. Thanks for adding this instruction.