Allow manual specification of dsn, or tnsnames without wallet

[enegaard]

Current connection mechanisms are not very flexible. I have a need to connect with tcps, but without doing client SSL authentication.

The only way I can see that this is possible today is to use a wallet to store both trusted certificates and credentials, but I would prefer not to have to store credentials in a wallet.

It seems like the most flexible way to handle this use case would be to allow manual specification of the dsn in all modules that perform connections.