Create mechanism to manage stylesheets

[juliendelplanque]

Matplotlib propose this feature, this should be integrated.

http://matplotlib.org/users/style_sheets.html#style-sheets

[jecisc]

This can help: https://github.com/pharo-contributions/Stylesheet

[juliendelplanque]

Sure, need to see how it can be integrated with Matplotlib's built-in stylesheets system. :-)