Finalize KPS5 model

[ufechner7]

• Implement the AKM interface
• Add the VSM model
• Add tests

See also: #149

[ufechner7]

TODO list:

1. Cleanup the example
2. implement power and depower
3. add default interface
   init!
   step!
   update_sys_state!
4. cache the simplified model
5. add a test case for depower
6. add a test case for steering
7. add in 3D viewer
8. add the VSM model