LiveEdit cannot handle new MSO mimeTypes

Adding the .xlsm mimetype to FF LiveEdit addon works, but LiveEdit refuses to handle it, since the correspondign mime type is not in its list of known mimeTypes.

Adding the Office 2007 mime types (see for instance http://www.bram.us/2007/05/25/office-2007-mime-types-for-iis/) to LiveEdit known mimeTypes list would solve that issue.

This issue actually prevents working on macro enabled 2007 documents in LiveEdit