Write a introductory tutorial for the docs

[Stefan Ecklebe]

The usage an work with the toolbox should be explained within a little tutorial.
It should start with the modelling of a simple system an its implementation, enriched with some formulas and code snippets from the related parts of the toolbox.
The next step would be an introduction to the GUI by simulating the freshly created system.
Furthermore, a simple control law can be derived and implemented to show the most basic components of the modular simulation loop.

Other sections would then focus on the simulation system in whole or parts like trajectory generation or observer design.
The result of the tutorial should be a complete example system that should also be added to the examples sub-package.

The introduction should have a lesson-like structure with little hints about the requirements to understand them.

Things that should be explained:

• What is the difference between the Solver and the Model?
• Why do the Model outputs do have a name and the Solver and Trajectory outputs only have numbers like .1, .2 etc.
• Why do strings in the property list do have to be entered with surrounding " "?
• How does the control loop look like?
• What does the ModelMixer do and what are its possibly settings?
• What are Post- and MetaProcessors and what do they do?