Document Fonts: Frescobaldi dialog and Wiki page

[Urs Liska]

Hi all,

I have for now completed my work on Frescobaldi's new Document Fonts dialog and 
would encourage everybody (who runs Frescobaldi from Git and uses LilyPond >= 
2.19.12) to test my Pull Request 
https://github.com/frescobaldi/frescobaldi/issues/1164. For those who have 
already tested this earlier, please note that this is a new PR on a new branch 
dev/urs/document-fonts.

It is intended (but not yet implemented) that Frescobaldi also allows 
downloading alternative music fonts from the Github repository 
https://github.com/openlilylib-resources/lilypond-notation-fonts. For this 
repository I would be grateful if people could help by writing a few Wiki pages 
about font handling in LilyPond.
Please come forward, this is a rare chance for *users* (without programming 
background) to give some support.

Best
Urs