Provide a convenient way to configure a Directory within the Spring extension

[templth]

Following this discussion on StackOverflow, it appears that configuring a Directory for Restlet within the Spring extension isn't simple at it seems, especially if we want to use the client protocol war.

See the discussion on StackOverflow: http://stackoverflow.com/questions/28775569/restlet-cant-locate-static-files-through-directory.

[thboileau]

I wonder if SpringContext may be part of the response: http://restlet.com/technical-resources/restlet-framework/javadocs/2.3/jse/ext/org/restlet/ext/spring/SpringContext.html