PDO DB Connector: Connect and execute common queries using PDO

This class can connect and execute common queries using PDO.

There is a base class that establishes connections to a given database using PDO. It has functions dedicated to connect to MySQL and Microsoft SQL server databases.

A sub-classe provides functions to perform common queries. Currently it can:

- Execute arbitrary SQL queries and return the results in an array
- Query a table and return a single column of results as an array
- Query a table and return all rows as an array
- Execute INSERT or UPDATE queries without prepared values
- Delete table rows that match a condition

tables
Maintain tables in a MySQL database