CombinedBuilderParametersImpl now supports a way of adding default parameters for child configuration sources.

To a parameters object an arbitrary number of child parameter objects can be
added. These parameters are copied to parameter objects for child
configuration sources. So this is a convenient way to set default properties
for child configuration sources of a combined configuration builder.

git-svn-id: https://svn.apache.org/repos/asf/commons/proper/configuration/trunk@1463685 13f79535-47bb-0310-9956-ffa450edef68
FileBasedBuilderParametersImpl.reloadingRefreshDelay is now of type Long.

The property can be undefined, therefore the value null makes sense.

git-svn-id: https://svn.apache.org/repos/asf/commons/proper/configuration/trunk@1463686 13f79535-47bb-0310-9956-ffa450edef68