Preliminary changes to windows installer script.
Fixed typo.
Windows installer: gave up on unicode collation.
More windows package tweaks.

Make sure subordinate packages are reinstalled.
MediaWiki reader:  Allow Image: for images.

Closes #971.
Markdown writer: Fixed bugs in YAML header output.
Tweaked windows install script.

Assumes that pandoc-types and pandoc-citeproc are in Hackage.
make_osx_package.sh: Assume pandoc-types, pandoc-citeproc are in Hackage.