The merge of cli , default and file config should be simplify.

[TwistedSim]

I have encontered some problems where the config is not initiated correctly when used in as class attribute.

At the moment, the merging of the config from those 3 place is a bit confusing, a ChainMap should solve this as it can be easily update with new config option. The order of importance should be: default < file config < cli arguments.