Make the config differ tests shared_examples

This will allow the subclasses to call the tests of the superclass without repeating all the tests. Also changed the name of the file to include to reflect what it now is.
Pass the type of Configuration Differ

So that subclasses are testing themselves rather than all just testing ConfigurationDiffer again. `?w=1` will help to see the changes in this commit as I also fixed indenting.
Make subclasses run the Config Differ tests