Support auto detection of the callers

Currently you have to specify which assembly is used as "internal feeling" source for the Conficius. Imagine you can create Conficius only by saying that you relies on AppSettings and Conficius knows who is asking for information and provides the requested information automatically choosing and reading the related configuration file. This patch introduces such a feature.
Can we name it a little better? It's hard, but maybe just `AppSettingsSource` to express that it is concerned about the settings of the main _App_.