parse sectext paragraph styles into class='centered'
improve handling of the form and formc styles:

* the form class was over-applied
* handle cases where a numbered paragraph and form text were merged into a single paragraph with a hard line break
* change the encoding to a <level> with type=form wrapping consecutive form/formc paragraphs, and formc becomes class=centered.
turn class="table", class="tablec", and class="PlainText" into a new <level> type "table" like for forms ("PlainText" is treated the same as "table")
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