Verbose server & proxy prefix

[jmacura]

Description

Port of changes done in the https://github.com/hslayers/hslayers-ng/tree/hsl-server-1-5 branch
Adds verbose option for hslayers-server.
Throws away any proxy prefix like "/proxy/" or "hslayers/proxy" etc.

Related issues or pull requests

closes #6028

Pull request type

Please check the type of change your PR introduces:

• Bugfix
• Feature
• Dependency updates
• Code style update (formatting, renaming)
• Refactoring (no functional changes, no api changes)
• Build related changes
• Documentation content changes
• Other (please describe)
• I am unsure (we'll look into it together)

Do you introduce a breaking change?

• Yes
• No
• I am unsure (no worries, we'll find out)

Checklist

• I understand and agree that the changes in this PR will be licensed under the [MIT License]
• I have followed the guidelines for contributing
• The proposed change fits to the content of the code of conduct
• I have added or updated tests and documentation, and the test suite passes (run npm test locally)
• I'm lost; why do I have to check so many boxes? Please help!