Create separate Xlsxwriter example that uses PyODBC

[abmusse]

The dbtoxlsx example as currently written is a good "works out of the box" solution for people who have no interest in coding or setting stuff up (they just want data in a spreadsheet).

Sadly, using ODBC adds more setup task and makes this example much less useful in a ready-to-use utility use case.

Until we can make ODBC out-of-the-box ready, we should instead just make a second flavor of the example

Originally posted by @ThePrez in #35 (comment)