Fix connection string conversion from ODBC to OLE DB

[lauxjpn]

• Fix connection string conversion from ODBC to OLE DB.
• Also introduce new database password (in contrast to workgroup user password) extension methods.
• Fix missing connection disposal in AdoxSchema.

There still exists an issue, because it seems that ODBC is using the PWD connection string option for both, the workgroup user password and the database password. It is also possible, that PWD only represents the database password, but then an option for the workgroup user password is missing.

I posted a question about this on StackOverflow:

• How to specify MDW username and password (user-level security) AND the database password (shared-level security) in an ODBC connection string?

Fixes #71