Do not store passwords in plaintext

[LoganTann]

Hello, I find this extension very useful. However, I need in very rare cases to access to production databases and I do not want to store such sensitive passwords in a config file.

It would be cool to add the following feature : option to not save the password, and to prompt the password when connecting.

[rosspatil]

@LoganTann my PR will resolve this issue #248 .

Happy to hear your feedback