Switch to absolute paths for styles and menu links.

This allows the menu to work also in pages not in the base directory.
Add missing style file to a few pages.
Remove unqualified calls to make_shared.

On VC++12, argument-dependent lookup was causing ambiguities
between boost::make_shared and std::make_shared when vectors
were passed among the arguments.

Thanks to Armel Wambou for the heads-up.