Allow online editing in Word documents

[lscorcia]

When opening a document using a ms-ofe hyperlink (i.e. ms-word:ofe|u|https://dgrob-lscorcia:8443/Luca/test.docx ), the server has to specify an additional header in the OPTIONS method to allow successful opening by Office applications.

Therefore, in file WebDavOptionsMethodHandler, after line 41, the following line should be added:

context.Response.AppendHeader("MS-Author-Via", "DAV");

This makes Office applications send LOCK and UNLOCK commands to the server and play nice with the WebDav implementation.