Added a test case for saving to a newly created file.

It is tested whether the allowFailOnInit flag is evaluated, so that a
configuration can be created and associated with a not yet existing file.
Later on, the configuration is saved to this file.

git-svn-id: https://svn.apache.org/repos/asf/commons/proper/configuration/trunk@1602502 13f79535-47bb-0310-9956-ffa450edef68
Reworked chapter about CompositeConfiguration in user's guide.

git-svn-id: https://svn.apache.org/repos/asf/commons/proper/configuration/trunk@1602503 13f79535-47bb-0310-9956-ffa450edef68
Reworked chapter about CombinedConfiguration in the user's guide.

git-svn-id: https://svn.apache.org/repos/asf/commons/proper/configuration/trunk@1602504 13f79535-47bb-0310-9956-ffa450edef68
Reworked chapter about bean creation in user's guide.

git-svn-id: https://svn.apache.org/repos/asf/commons/proper/configuration/trunk@1602505 13f79535-47bb-0310-9956-ffa450edef68
Renamed member fields to be compliant with Java conventions.

git-svn-id: https://svn.apache.org/repos/asf/commons/proper/configuration/trunk@1602506 13f79535-47bb-0310-9956-ffa450edef68