Xlsx conditional styles cannot be used to change alignment, nor font family, nor font size.
Conditional::getStyle currently allocates a new style as an unconditional style; it is changed to do so a conditional ctyle.
Border should not be conditionally merged if borderStyle is OMIT.
Inline Css was generating `class="gridlines gridlinesp"` for all cells. It is changed to use the worksheet settings to decide which classes to use.
Fix#4539. Conditional Formatting was recently added to Html Writer. It works fine when not using inline Css. However, when using inline Css, the code inadvertently added 2 different `style` attributes (one for the unconditional style and one for the conditional style) to the same cell. This is not valid html, and results in losing the conditional styling. This PR combines the two `style` attributes into one, which will now come after the `class`, `colspan`, and `rowspan` attributes.
Aside from the new tests, this PR changes an unusually large number of existing tests. While this might normally be considered a red flag, it is not a problem here. All of the changes involve merely changing the order of attributes within html tags; none of them affect how the generated html would appear in a browser.
While researching issue #1551, I came across some minor problems.
When a spreadsheet does not have a title, which is often the case for spreadsheets created with Excel (note that this is not the case for spreadsheets created with PhpSpreadsheet), if you try to save it as Html, it throws an exception. It will now use the sheet title of the active sheet as a title in this case.
When writing an Html spreadsheet using `useInlineCss(true)`, gridlines are not handled properly. This is addressed by adding `class=gridlines gridlinesp` to the cell's `td` tag, and by suppressing any border attributes which would be styled as `none #000000`. It would be unusual to turn off gridlines for specific cells, but that can still be accomplished by using `Border::BORDER_NONE` in conjunction with any color other than `#000000` - see new test `testHideSomeGridlines`.
oleibman