feat: initialize server side google analytics with multiple options

[asastre]

Update for Google Analytics plugin

When tracking from server side sometimes is needed to share the clientId created in the browser so the tracking on both sides (browser and server) represents the flow done by the same user.

Now, the Google Analytics can be initialized on the server side only with the trackingId, not being able to specify a clientId, but the universal-analytics library accepts more options on its initialization, including the clientId, userId, etc.

This PR enables the possibility of initializing the Google Analytics on the server side with all the possible options that universal-analytics accepts and also mantaining the actual configuration.

[DavidWells]

Thanks for the PR! ❤️

Added a couple of notes