API update with changed models

[kevinpapst]

Hi!

I had to refactor the Kimai API and smooth out some details.

At least some of your models are now outdated in (eg. all the duplicate ones with numbers at the end, Team1 Team2 ):
https://github.com/kbancerz/kimai-python/tree/master/kimai_python/models

Please have a look at kimai/kimai#1826 and run some test, especially on the routes that have deeper nested objects. I gave my best to avoid BC breaks in the JSON result, but I changed a lot within the serialization layer and unfortunately not every attribute was covered with tests before (now they are).