Make mrcfile.validate silent

Hi.

I have a small suggestion for improvement. Would it be possible to make the printed output of `mrcfile.validate()` optional in case I am just interested in a bolean return value?

Best and thanks,
Chris

Start by locating the mrcfile.validate() entry point and checking how it currently prints output and returns validation results. Done means callers can optionally suppress printed output while still receiving the boolean result; verify the existing validation behavior remains unchanged.

Written by the indexing model from the issue text.