* 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.
Continuing the work from #2828, #2841, #2846, and #2852. This is probably my last change in this area for a while.
Bubble charts can have bubbles of different sizes. Phpspreadsheet had not supported this. Openpyxl comes with sample code to generate such a chart. I was especially drawn to that solution because its namespace usage would have been unexpected before 2852. And it turned out to come with other surprises - use of absolute paths in the .rels files (PhpSpreadsheet expected only relative), use of a one-cell anchor to place the chart (PhpSpreadsheet expected two-cell anchor or absolute positioning), plaintext in the legend (Phpspreadsheet expected RichText), no cached values for chart data. Excel handles the file okay, and this PR makes sure PhpSpreadsheet does as well. This file is now Samples/Templates/32readwriteBubbleChart2, and is used for both generating a sample output file and in formal tests. A new sample in the 33* series demonstrates how to code these.
oleibman