new export options
- fixes for 1024 res (horizontal scrollbar and list node wrapping)
- Moved 'View' primary level option to 'Go', since that menu contains links to 'destination' screens (thanks to Martin Dittus for pointing out this abuse of the OS X 'View' menu convention).
- Added 'plain text' export option
- Added 'web page' export option
- Labelled 'opml' export option (previously default)