Demo showing the organization of an exercise for the mailhandler.
Note that not all the implementations of members/constructors in the class
Strings are provided: that's not necessary if the exercise doesn't ask for it.

This demo also doesn't use an inline function implementation file: it could
have been used, in which case the order.txt file would start like this:

    descr.txt
    strings/strings.h
    strings/strings.i
    strings/strings.ih 
    ....

The pdf constructed from this demo is strings.pdf and can be downloaded 
from the same location as the current zip file.
