Resolve "Skip in Green"

Release notes

Introduce a green [ SKIP ] label if a sample is supposed to be skipped.

Details

In order to not needlessly alert the user by printing in pink color, the green label shows that everything is ok at first sight, but still informs that a sample has been skipped. In general, we want that

Label	Color	Used when
OK	green	File is found and everything is ok.
SKIP	green	File has been processed before by TQMultiChannelAnalysisSampleVisitor and the user does not need to be alerted that it has been skipped.
SKIP	pink	The user specified that files should be skipped (eg. using the --restrict option). Then the pink color is a reminder.
WARN	yellow	Error that is potentially not dangerous.
FAIL	red	Something is seriously wrong.

Closes #149 (closed)