Usability enhancements for the Export Screen

[Jonathan Thomas]

The export screen needs the following enhancements, to help with usability:

1) When selecting the various dropdowns, it should automatically select the first item in each subsequent dropdown. In other words, it should cascade the dropdown boxes once you select the first value.

2) The export screen needs to be smaller. There is lots of unused white space, due to some expanded advanced panels. The advanced panels need to be collapsed to regain the white space.

3) When the "Upload to Web" feature is selected, it should auto select the corresponding profile and settings.

4) The export screen has errors on Ubuntu 9.10. These need to be fixed.

[Jonathan Thomas (jonoomph)]

All of these changes have been made, and the export screen is much easier to use. The method of displaying missing codecs is also improved. It uses an "InfoBox" at the bottom of the screen, which is less annoying that pop up messages.