* Charts Additional Support for Layout and DataSeriesValues
The dLbls tag in more or less the Xml equivalent of the Layout class. It is currently read and written only for the Chart as a whole. It can, however, also be applied to DataSeriesValues. Further it has properties which are currently ignored, namely label fill, border, and font colors. All of these omissions are handled by this PR. There are other properties which can be applied to the labels, but, for now, only the 3 colors are added.
DataSeriesValues can have effects (like glow). Since DSV now descends from Properties, these are already supported, but support needs to be added to the Reader and Writer to handle them. This PR adds the support.
* Add Unit Tests
Based on new samples.
* Minor Improvements
Slight increase to coverage.
Because even if it doesn't make a difference in practice, it is
technically more correct to call static methods statically. It
also better advertise that those methods can be used from any context.
oleibman
Adrien Crivelli
Gabriel Caruso
Zharikov Viktor