Legend in case of using Name property

[FoggyFinder]

From documentation:

A legend is added automatically when names are used for data sets.

That's incorrect right now.

Probably because

let hasLegend = not (String.IsNullOrEmpty series.Name) || LegendEnabled.IsSome

series.Name is empty since #21

[voronoipotato]

dce9fec

does this check-in fix this issue?

[FoggyFinder]

@voronoipotato no.

Probably I wasn't clear enough.

96e4f6c

Name was set to a Chart, but legend's visibility still depends on name of a series.

let hasLegend = not (String.IsNullOrEmpty series.Name) || LegendEnabled.IsSome

So, I see two options here:

1. Documentation is wrong
2. hasLegend should check ch.Name instead of series.Name.