Removed obsolete FileSystemBased interface.

The interface was mainly used by classes derived from
AbstractFileConfiguration which no longer exists.

git-svn-id: https://svn.apache.org/repos/asf/commons/proper/configuration/trunk@1521599 13f79535-47bb-0310-9956-ffa450edef68
Added new FileLocatorUtils helper class.

This internal helper class provides functionality for locating configuration
files based on different search criteria. Initially, some methods of
ConfigurationUtils have been copied over. The next step is to remove these
methods from ConfigurationUtils and to point calling code to the new class.

git-svn-id: https://svn.apache.org/repos/asf/commons/proper/configuration/trunk@1521600 13f79535-47bb-0310-9956-ffa450edef68