[Qgis-developer] WIP: Redesigned gradient editor with interactive plot

[Nyall Dawson]

Just realised I hadn't announced this work on the list yet....

You can see some work in progress videos here:
https://www.youtube.com/watch?v=0UuZWTArKj0&feature=youtu.be
and
https://www.youtube.com/watch?v=v0mkqUXeOnc&nohtml5=False

Still to add is a preview of how the gradient will look as discrete
classes. I'm struggling with the vertical height of this new dialog,
so any suggestions on the layout would be appreciated!

Nyall