config: alphabetically sort the channel list

Change-Id: I86af25601794e55cadf5fa2636110bd8fc98cd97
config: fix yaml indentation

js-yaml is giving me some error messages related to how the yaml files
are indented:

    JS-YAML: deficient indentation in
    "config.yaml" at line 71,
    column 5:
	    ]
	    ^

Reindented both config.yaml and config.yaml.sample.

Change-Id: If24c567468dd9a1270acd110ffaa3304ed9e6f48