[gh238] [bz5667423] support for multiple application configuration files

Continuation of PR #898.

By specifying the list of files to aggregate with the application.json, developers will have the flexibility to split the application configuration into various files, e.g:

```
[
    {
        "settings": [ "master" ],
        "applicationConfigFiles": [
            "node_modules/devices/application.json",
            "relative/path/to/custom.json"
        ],
        "testKey1": "testVal1",
        "testKey2": "testVal2",
        "testKey3": "testVal3"
    }
]
```