GDP: introducing examples

[Graham Percival]

Currently we have a few different ways of introducing examples in the 
docs.  Should we standardize on a particular way, or just let doc 
writers do whatever they want?

Currently we have a combination of four different ways.

1)  The text just continues directly into

        c'4\mf

2)  The text suggests that one may do foo,

        c'4^"foo"

3)  The text directs the reader to the following example:

        << c'4 { e g } >>

4)  The text forms a complete sentence.

        c'4^-\mark \default


Should allow all?  Specify one method?  Disallow one or two methods?
- Graham