Homogenize and improve Javadoc, particularly <p> tags:

[nipafx]

Proposed commit message:

Homogenize and improve Javadoc, particularly `<p>` tags:

* leading paragraphs don't need `<p>`/`</p>` tags
* all subequent paragraphs need `<p>` *and* `</p>` tags
* `<p>` and `</p>` tags are on the same lines as the content
* paragraphs end with an end-of-sentence symbol
* a paragraph is always surrounded by empty lines (one before
 and one after)
* move `<ul>` blocks out of `<p>` blocks

Other changes:

* remove `<code>` tags when they don't contain code
* fix capitalization of feature names (they're no proper nouns)
* probably more that I forgot

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Documentation (general)

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[Bukama]

I really like such clean up work! Thank you very much.
Changed your proposed commit message about "the two lines" as communicated on stream and will merge now.