[Development] ColorMap class

[hugo winter]

Hello,

I just wrote a ColorMap class for QtChart. It's part of a GUI project
developedat the Laboratory of Plasma Physics (LPP / http://www.lpp.fr )
to visualize satellite data.

While the work is still in progress, I'd like to have some feedback
about it.Also, I'd like to discuss the possibility to integrate it, at
some point, into the QtChart API.

I'll be happy to make any changes from comments you may have.

I would also be thankful if you could give me some advices about some
troublesome points :

- I had hard time trying to implement a custom axis to display a
colorbar. Although functional, our actual implementation is a bit
crapy.Is there a way to change the place where Ticklabels of
QAbstractAxis are painted?
http://imgur.com/Bu7wU1Q

- I noticed that the colormap is somehow disappearing when multiple
lineseries are added to the chart.It appears back when refreshing the
painting process. Is this a known bug (it might come from an hover
event) ?

You can find the code here:
https://hephaistos.lpp.polytechnique.fr/rhodecode/HG_REPOSITORIES/LPP/u
sers/hugo/ColorMapChart

In order to try it, you may look at :
qtcharts/examples/colormap/sources/main.cpp

It is under GPL.

Thanks.
Hugo