Expose one more bit of style information generically (for XSSF). If someone needs all these properties for HSSF charts as well, we can build a new Interface for the various bits and populate it with things like axis line width and color, etc. but for now I think most users are in the XSSF realm like me.
Standardize some more common chart axis properties.
Implement the ChartAxis ss interface for date axes, which are pretty much a category axis with one extra property, a date granularity (not currently passed through, get it still from the CT* class). Created the class and test from the category axis versions.
git-svn-id: https://svn.apache.org/repos/asf/poi/trunk@1798414 13f79535-47bb-0310-9956-ffa450edef68