Added preliminary support for DSN. Refs #4396

@markstory @AD7six thoughts on moving this into a Trait within the Core namespace and also adding it to Cache and Log?

- [x] Cache
- [x] Database
- [x] Email
- [x] Log

I think you may be able to use an escape code for it, but for people with `@` signs in their passwords, they can just not use a DSN.