Implementation of nested skills

[maikenp]

As discussed with @vingar and @caela we want to categorize the skills in the following way

skills:
   - prog_lang:
      - python
      - c++
      - someprog 
   - skilltype2:
      - pps
      - cmake

At the moment expanded the skills_found to a dictionary instead of a list as it was before.
I am also printing out the people found - I think that makes sense, not only to see where people are in the map. But we can discuss this.

What I implemented also is a dictionary holding the skill-keys and values, so instead of showing the skill-key in the All skills section one can have a more meaningful and prettier category:
{'prog_lang':'Programming languages','skilltype2':'Some other skill'}

This is how it looks with the changes implemented:

Merge request: #2