Allow URL encoded name/password in DSN connect string, enabled via an option

In order to pass a username or password in the DSN string that has special characters within it, say an @ symbol, the driver needed some mechanism for encoding/decoding the strings.

I added an option to the DSN driver to enable decoding of the username/password credentials.  To use it, the caller passes encoded=true on the DSN line (e.g. user/pwd@server:port/sid?encoded=true).  When that option is set, and only when it is set, the driver will pass the credentials through the url query parameter decoder before connecting to the Oracle system.