feat: Vehicle Routing: allowsUnassigned

[TomCools]

Description of the change

Solves part of #326

Additionally:

• Make the color of the visits match the assigned vehicle (instead of blue).
• Replace the ugly crosshairs with houses
• Support "unassigned" as a better option in recommendations

Checklist

Development

• The changes have been covered with tests, if necessary.
• You have a green build, with the exception of the flaky tests.
• UI and JS files are fully tested, the user interface works for all modules affected by your changes (e.g., solve and analyze buttons).
• The network calls work for all modules affected by your changes (e.g., solving a problem).
• The console messages are validated for all modules affected by your changes.

Code Review

• This pull request includes an explanatory title and description.
• The GitHub issue is linked.
• At least one other engineer has approved the changes.
• After PR is merged, inform the reporter.