Backported Bob's EPUB3 changes to EPUB2 from r9740 -> r9742 -> r9743:

Backported Bob's EPUB3 changes to EPUB2 from r9740 -> r9742 -> r9743:

* Implement base.dir/OEBPS using internal chunk.base.dir instead of
  new param epub.base.dir.

* Additional changes, specific to this stylesheet:
  - Construct parameter epub.metainf.dir from base.dir + 'META-INF/'
  - Changed parameter epub.cover.filename epub.oebps.dir to
    chunk.base.dir
  - Template opf: concat base.dir with epub.opf.filename
  - Replaced two subsequent xsl:value-of's with concat()