Re #9647. Added docs-qthelp target.
Re #9647. Adding back in install information for qthelp.
Re #9647. Fixing up the web files that are installed.
Re #9647.  Adding in missing installer bit for windoze.
Re #9647. User has to pick either html or qtassistant.
Re #9647. Changing buld scripts to point at new target.
Re #9647. Fixing the build script.
Re #9647. Making docs-html something that is optionally buildable.
Merge remote-tracking branch 'origin/feature/9647_qthelp_target'