frontend: initial commit of the frontend

We are committing this stuff because it is simpler to review and ameliorate it in tree
Change comments
Move files of /source in /backend
Remove /source
Change README.md
Organize public data and utilities
Network neutrality in www
_makeplot.py in utilities
Remove public folder
Add index.html
Remove Network_Neutrality.html
Adapt index.html to retrieve data with the new directiories configuration
Move /var in /frontend
Improve router functionalities
Web server and API response to the same port
Modify NeuViz API call by the d3.js viz
Clean unnecessary code
Remove unnecessary else
Update documentation. First information on the new frontend
Add .gitkeep file to data directory

To remind us that we want to keep such directory but we don't
want to consume too much space at github.