Refactor learning pages

[aschaal]

• It's a but confusing what pages are needed to first setup.
• Some CMake commands are outdated.
• Pages like the "Managing the lifecycle of components" goes to deep in some details of referenceApp without explaining the idea and the general concept.

So, here is my proposal:

• First, fix outdated things.
• Add a section for "First Steps" (not really learning, but what to do for first compilation and running)
• Split "Learning" and "Concepts" into separate sections (with the blue captions)
• Reduce referenceApp specifics (only as example) and explain the background in more general