New features in GVD 2.0.0

- Support for C++ methods in the file explorer.
- A new multiple document interface (MDI) is provided.
- Preferences handling has changed, and the old preferences file is no
  longer compatible. On Unix system, please use the following script to
  convert the file:
     cat ~/.gvd/preferences | tr ':_' '-' > /tmp/gvd_pref
     mv /tmp/gvd_pref ~/.gvd/preferences
  On windows system, edit the preferences file by hand, and replace the
  semicolon and underscore characters by minus signs in all the XML tags.

