[osis-core] <chapter> needs to be a child of <p> (and probably other elements.

[Todd Tillinghast]

All,

Because we are using <chapter/> as a milestone AND because chapters
start in the middle of paragraphs <chapter> MUST be allowed to be the
child of <p>.  This is case occurs once or twice per Bible, depending on
the translation.

It also possible for a chapter to start in the middle of other elements.
Because these cases seem unlikely, I think we should ONLY allow
<chapter> as a child of <p> for the current release.

Adding <chapter> as a possible child of <p> will allow the following
structure:

<div type="book">
	<div type="section">
		<p>
			<chapter>
				<div>
				</div>
			</chapter>
		</p>
	</div>
</div>

Todd