Merged pages retain TOC position

Meaning: you can start a level2 indented TOC item/link/page with level1
header and sections and they will be automatically increased to reflect
the indention from the TOC.
Bump Version.
Use dw2pdf internal engine

Added the option to use the dw2pdf export PDF files. Meaning you can
use the already created templates for dw2pdf by just selecting the
dw2pdf renderer. Siteexports PDF features (like templates) will be
disabled.