Allow JURI to be injected nice, but...

I'm not to sure about this as when DI is implemented all injected JUri instances would be a shared instance of the current request (Currently `JFactory::getUri();`). But for the time being doing `new JUri` isn't making it possible for my `https` site to load Google maps as the scheme on an empty JUri instance is `null`.

There is another way of doing this which would be modifying JUri setting the construct to accept 'SERVER' and then `$this->populateFromServer();`