Web-GSoC: Remove Grace note project (issue 317210043 by address@hidden)

[dak]

The problem with "mentoring" this is that the expertise for successfully
mentoring this project is the same as for doing it yourself.  This is
not a question of making a plan and then implementing its parts over the
course of several weeks.

Either an idea works or not.  And it needs to be tied a whole lot into
LilyPond's internals to work.  Anybody wanting a dozen dead branches
that worked _not_: I have some lying around.

So this really is not a student level problem, or even a master level
problem where having a student to do boring parts would help.

https://codereview.appspot.com/317210043/