Revert "Removed extra body tag from epub3 template."

This reverts commit 7ff2baf592ee4627da0ad1e5cec60e6be3de5785.
Revert "epub, epub3: Added id="cover" to body of titlepage."

This reverts commit 63443da4501728332a6624a1d1b769ef9183436b.
epub templates:  insert id="cover" in body of cover page.

We check for the coverpage variable.