Add support for LineChart in Framework

[akhil0]

Hi, I am trying to create a burndown chart and would like to know if it's possible to add Line Chart as component in the framework. It would be very helpful.

[plouc]

@akhil0, you should consider using an external package, see https://github.com/SC5/mozaik-ext-analytics for reference.
Perhaps I'll add a Line Chart later by including another package I'm working on https://github.com/plouc/nivo, but for now the best option is to use a dedicated lib.