* Add Support to Chart/Axis for Glow/SoftEdges
Chart is very under-covered in unit tests. I was hoping to just add some tests and be done with it, but that just won't suffice - many code changes are required. Adding Glow properties for Axis turned out to be a real mixed bag - no support in Xlsx/Reader at all, support in Xlsx/Writer ... for the X-axis only. So we'll just inch forward in many stages.
This change does not address other Axis properties (Fill, Shadow, Line, LineStyle, and maybe others, and their sub-properties). On my to-do list.
GridLines, and maybe other Chart objects, also should support these properties. This change does not address those. On my to-do list.
No support is added for spreadsheet formats other than Xlsx.
* Refactoring
This should make the code easier to follow, and I hope it will also be extensible to other object types (e.g. GridLines).
* More Refactoring
Make scheme/srgb easier to handle.
* Fix Typo
In a very rarely used function.
oleibman