MDL-34841 error importing questions with long names.

MDL-34841 error importing questions with long names.

The problem was with the non-UTF-8-safe way that a question name
was being constructed from the question text.

I have done a proper fix with methods in the base class to
carefully construct a question name that is reasonable, and
which will fit in the database column. Then I have changed all
importers to use the new methods.

I also remembered not to break the lesson in the process.