Implement non-standard tuplet numbers

Implement non-standard tuplet numbers

-) Add function for different fraction than the actual tuplet fraction
-) Add wrapper function that appends a note with given duration after
   the standard tuplet text (denominator or fraction)
-) Add function to print tuplet text with both fraction values with a
   note duration attached
-) Add snippet to be included in the Docs
-) Add regtests for all these cases
-) Remove definitions from musicxml2ly and make it use these new functions