Console badge should not be visible when rendering offscreen

[mwestphal]

Describe the bug
F3D now has a console and associated console badge to display log and control F3D.
However, this is inherently a feature for interactive usage of F3D.
The console badge especially, should never be shown when doing offscreen rendering with --output.
Alternatively, the whole console could be disabled until we are using f3d interactively.

To Reproduce
Steps to reproduce the behavior:

1. Open the file using f3d file_with_warnings.ext --output=a.png
2. a.png contans a visible badge, not usefull and can causes problem for user rendering frames

Expected behavior
No console badge unless rendering interactively

F3D Information
Paste the content of f3d --version: master

Additional context
Add any other context about the problem here.