ClsMySQL: MySQL database access wrapper

This class implements a MySQL database access wrapper.

It implements a singleton that concentrates the access to a MySQL database access in a single object.

The class can perform the usual database access operations like establishing database server connections, executing SQL queries, retrieving results into rows or objects, getting the number of result set rows, or the number of affected rows or the last inserted identifier, executing INSERT, UPDATE, DELETE and DROP queries from parameter lists, managing transactions. etc..