Warn user if colourspace has to be assumed

[LightArrowsEXE]

If any of the colourspace options (matrix/transfer/primaries) are set to 2, vspreview should warn the user that it has to assume the colourspace. This should imo display an error messages as such:

For example, 720x480 video:

WARN: The colorspace is unknown (2/2/2)! Assuming 6/6/6!

There are probably better ways to phrase this, but I want to get the following ideas across:

• The colourspace as it's currently tagged (in case i.e. matrix is tagged, but nothing else is)
• What it's assuming them to be right now.

As an extension, this should maybe also be included in vstools.initialize_clip, if only for transparency's sake. Maybe even make it a part of the function that tries to guess a colourspace based on heuristics (behind a strict param)?

[Setsugennoao]

I don't like the idea of logging that. What about integrating it in the props tab.

[Vodes]

As it stands currently, the side menu is still entirely undiscoverable and having a log output would be immediately noticed

[ghost]

+1 for warning