switch the property/field templates over to use the 'navigation' approach by default?

Once this PR is merged and issue fixed https://github.com/joel-costigliola/assertj-assertions-generator/issues/67 along with the NavigationListAssert class in assertj-core: https://github.com/joel-costigliola/assertj-core/issues/641 it would be easy to switch the OOTB templates in the generator to use the 'navigation' model approach.

So that for every property of an object we generate exactly one navigation method that lets users chain assertions together; reusing all the methods from ListAssert and NavigationListAssert for iterable properties or the custom typed assertions for other properties.

This would result in much smaller code generated for the assertion classes and much more power. The only downside is some of the current methods would be a tad more verbose.

e.g. for a generated assertion class with a name property the current generated code would be:

``` java
// current generated code
assertThat(person).hasName("James");

// new minimal code
assertThat(person).name().isEqualTo("James");
assertThat(person).name().contains("m");
...
```

Ditto for iterable properties right now we generate a few methods which are mostly already included in ListAssert. e.g. all these assertion methods are available on any generated iterable property method:
https://github.com/jstrachan/assertj-core/blob/7b1d079edeb5ac984cebbed77a65025718ee7673/src/test/java/org/assertj/core/navigation/ListNavigation_Test.java#L56-L62

Removing the old generated methods would break folks code I guess; so maybe we should add a flag to switch to the new more concise model?

If you are interested; here are the 2 new templates (which need minor tweaks to reuse the https://github.com/joel-costigliola/assertj-core/issues/641 code):
- for general properties/fields: https://github.com/jstrachan/fabric8/blob/5f99b82696856e9c5614ff5a728adfbeaab96751/components/kubernetes-assertions/src/main/assertj-templates/navigation_template.txt
- for iterable properties/fields: https://github.com/jstrachan/fabric8/blob/6e333451afceec3308e6869f39a14c3e569d837b/components/kubernetes-assertions/src/main/assertj-templates/has_elements_assertion_template_for_iterable.txt

Beginne mit der Prüfung von Issue 67 und assertj-core issue 641 und vergleiche anschließend die beiden verlinkten Navigation-Templates mit den aktuellen Property- und Iterable-Templates des Generators. Ermittle, wie die Unterstützung für NavigationListAssert und ein Kompatibilitätsflag die generierten APIs beeinflussen, und verifiziere, dass die generierten Assertions die Navigationsmethoden bereitstellen, ohne bestehende Methoden zu beeinträchtigen.

Vom Indexierungsmodell aus dem Issue-Text verfasst.