Update private, "internal" and public members to meet conventions.

Comments to separate each section (private, "internal", public).

A single var declaration for all simple private class variables.
Hmm, I think I forgot where I was and I thought it would be useful to have Chart.addSeries()  I agree that it's not great to be public on Axis since you add axes to series and not vice versa.

I'll undo the change.