Consolidate configuration files

#### What's this PR do?
Adds functionality that allows configuration files to be autoloaded from a single location

#### Where should the reviewer start?

*server.js* - This is where the config is loaded
https://github.com/desmondmorris/ds-mdata-responder/blob/consoldate-config/server.js#L10

*app/config/index.js* - The new base config file with auto loader at the bottom
https://github.com/desmondmorris/ds-mdata-responder/blob/consoldate-config/app/config/index.js

#### How should this be manually tested?

The config/index.js will load all of the config files within that directory and set the result within the app configuration object.  So for example, if you place variables.json in app/config, a configuration variable named "variables" will be set with the contents of that file.

#### What are the relevant tickets?

Related to #44