Reconsider component inheritance

[klafbang]

Inheritance should not be used for code sharing, instead use composition. This is a generic principle (https://en.wikipedia.org/wiki/Composition_over_inheritance) but in particular true for Angular components.

Now all/most components participate in an inheritance hierarchy. They do this by declaring abstract components. This is a code small and should be avoided.

If truly necessary to share functionality, instead create a service injecting what is needed, then inject that into components. This will also make the code shorter as we no longer have to autowire a ton of unnecessary services into all components to pass to the parent.