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

We can provide a cli utility to show what the parsed dsn would look like? I'd say a website, but letting people submit their database credentials is a bit lulzy.