Workaround for helpauthoring macros for Windows

[Regina Henschel]

Hi all,

the macros in the helpauthoring extension do not work with Windows 
native file picker, because the directories are not properly extracted 
and stored. I have attached a macro with a workaround to 
https://bugs.documentfoundation.org/show_bug.cgi?id=43021

If this workaround does not harm other file picker versions, I suggest 
to adapt the macros in the helpauthoring extension in a similar way.

Please test it and then say, whether you agree, that we should adapt the 
macros of helpauthoring.

Kind regards
Regina