Resolve "Naming and order of file->export menu items"

Under File, "Export Video View" has been renamed to "Export View Video" and moved two lines down in the menu. The layout in the export docu has been adjusted accordingly.

Reviewer Checklist

General code quality

• naming conventions are met (see .clang-tidy for detailed information)
• no static analyzer warnings in new code parts (e.g., use clang-tidy for checking)

General usability

• old versions of pet-files are still loadable
• documentation updated (if applicable)

Only if changes in UI

• new elements are also saved and loaded from pet-file
• check if tab order is still correct
• all new SpinBoxes are promoted
• new keybindings added to Petrack::keyBindings()

Closes #455 (closed)