Add a URL parameter for the `iframe` mode, e.g., hiding the hamburger button

[sehilyi]

There are some use cases for using Chromoscope with iframe, and I think we need to simplify the application for such use cases (cBioPortal integration and the Chromoscope Python package). For example, we need to hide the hamburger buttons in cBioPortal. We may also want to remove "Chromoscope" label and instead only show visualizations with minimal padding.

Use a URL parameter something like minimal_mode=true?