Add discussion of lexical conventions to tutorial

[julianhyde]

A user commented 'I was surprised to discover that I needed the "" around the table name'. The tutorial https://github.com/julianhyde/optiq-csv/blob/master/TUTORIAL.md should have a discussion of Optiq's lexical conventions, how to change them, and how ORACLE is the default; therefore you need double-quotes around a lower-case table name.