It was using select menus for the convenience of the code, but the
inconvenience of users.
The way this fix is done is a bit hacky, but it works, makes users'
lives much better, but it would be good if someone would dehackify
this in the future.
In 2.0 we had reduced the types of restore operations where we allow
to load the section names and section descriptions, only proceeding
when restoring to new course or to existing course, deleting.
With this patch, we change to the old 1.9 way, that was to restore
the section information always, no matter of the type of restore
operation (course restore, import, to new or to existing course,
deleting or adding). The only exception is that it's always checked that
the target section names and descriptions are empty.
