Add new comparison helpers to ValuesWrapper.
Cleanup whitespace.
Change `completeConfiguration` to support merging multiple configs.
Rename `getOptimizer...` to `createOptimizer...`.

The change in the prefix verb emphasizes that every call to the method
creates a new `ConfigurationOptimizer` instance instead of just
returning a cached one.
Refactor shared tutorial parts into their own files.
Add `Customizer` tutorial.
Add links to new tutorials.
Add some missing error handling to `Customizer` tutorial.