Instructions for creating the sample database used in SQL lessons.

This replaces #702, which had a lot of other things folded into it - undoubtedly could have cherry-picked the necessary changes, but merging one file seems simpler.  All credit for this work goes to @rkiko and @svaksha.
Merge pull request #728 from gvwilson/adding-sql-setup

Instructions for creating the sample database used in SQL lessons.