Add color-voices.ly (replacement for voice-colors)

This is a more generalized version of the voice coloring snippet,
without the directions coloring.
Add color-directions.ly

This is an offspring from voice-colors.
Unfinished.
Remove voice-colors.ly

This snippet has been separated to two snippets:
- color-voices.ly
- color-directions.ly
display-grob-anchors: Remove text option

Displaying a grob name is a different task and will be
realized in a separate snippet.
Add display-grob-names.ly

This snippet has been extracted from the
display-anchor-points snippet