* Charts - Add Support for Date Axis
Fix#2967. Fix#2969 (which had already been fixed prior to opening the issue, but had added urgency for Date Axes). Add ability to set axis type to date axis, in addition to original possiblities of value axis and category axis.
* Update 33_Chart_create_line_dateaxis.php
No idea why php-cs-fixer is complaining. It didn't do so when I first uploaded. I can't duplicate problem on my own system. Not enough detail in error message for me to act. Grasping at straws, I have moved the function definition (which is the only use of braces in the entire script) from the end of the script to the beginning.
* Update 33_Chart_create_line_dateaxis.php
Some comments were mis-aligned. This may be related to the reasons behind PR #3025, which didn't take care of this because this script had not yet been merged.
Unit testing now results in 100% coverage for Axis and Properties. All the properties in methods in Gridlines were more or less duplicated in Axis, and these duplications are moved to the common ancestor Properties. So, there isn't anything left in Gridlines. PhpSpreadsheet Chart is now over 85% covered (it was below 35% until recently).
Properties are in many cases set to default to null/null-string, rather than the default values they receive from Excel, and are not written to Xml if unchanged. This is consistent with how Excel behaves. A new property `crossBetween` is added to Axis, and, with support for that added to Xlsx Reader and Writer, some minor Sample peculiarities are corrected, in particular, the charts were sometimes slightly truncated on the left and right edges.
oleibman