This PR expands on PR #2195 from @nkjackzhang. That PR has been stalled for some time awaiting requested fixes. Those fixes are part of this PR, and additional tests and samples are added. The original request was to handle `vertical-align:middle` in Css (Excel uses `center`). This PR does its best to also handle vertical alignment Excel values not found in Css - `justify` (as `middle`) and `distributed` (as `middle`). It likewises handles valid Css values not found in Excel (`baseline`, `sub`, and `text-bottom` as `bottom`; `super` and `text-top` as `top`; `middle` as `center`).
It also handles horizontal alignment Excel values not found in Css - `center-continuous` as `center` and `distributed` as `justify`; I couldn't think of a reasonable equivalent for `fill`, so it is ignored.
The values assigned for vertical and horizontal alignment are now lower-cased (special handling required for `centerContinuous`).
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