Closes #3935

✌️ What does this PR do?

• Changes the visualizations module to take the module root path from the module configuration. To set a visualization as the home include a "home": true option in its configuration. Note that if several visualizations are configured as home, only the first one will be taken into account.
• Adds an integration test
• Adds a fix to avoid exceptions if a path is requested for a visualization not configured in the module settings
• Adds the route '/' to visualizations homepage. [front]

🔍 How should this be manually tested?

Configure GobiertoVisualizations as the home module in the site.
Change the module settings and include in a visualization the "home": true setting
staging

👀 Screenshots

Before this PR

After this PR

Does this PR changes any configuration file?

No

(Changes in these files might need to update the role in Ansible)

📖 Does this PR require updating the documentation?

Suggestion added to gobierto.readme.io