Improve documentation for "Extending the IVI"

Some input I've received so far:

1. https://doc.qt.io/QtIVI/extending-qtivi.html is out of date and needs to be rewritten
2. Vladimir mentions that in "Dynamic Backends" we don't really explain what we mean by "service"
3. Verify that the "Production Backends" mentioned in the documentation are actually in the diagram
4. Vladimir suggests having a section where both static and auto generated API development approaches are a kid of "compared" (makes sense for 1) (static APIs are good when you have a complex business logic, for example. and auto gen API are good when you have a service where you just write and read some values and send some commands)