Add ConfigurationAwareProvider interface.

Providers implementing this interface get access to the
ConfigurationFactory during bootstrap phase, can consume properties
from the factory and build custom configured objects.
Add a config loader for the classpath.

Allows loading a properties object from the classpath and expose the
result as a Map suitable for a Configuration factory.

Also remove the private toMap() method from ConfigurationLoader (replaced with Guava code).
Use RollingFileAppender from Logback core for http request log