ColorPicker scroll behaviour

[nicolaskruchten]

• If a ColorPicker is open and your mouse is not over the picker, you can't scroll the pane.
• If a ColorPicker opens at the bottom of a panel, it's not visible and it's hard to scroll into view

I think ideally the colorpicker should open inline like the new colorscale behaviour, instead of popping over.

/cc @cldougl