Add method that processes links and adds analytics data

[chrispenny]

Is your feature request related to a problem? Please describe

Relates to this issue in our Search UI:
silverstripeltd/silverstripe-discoverer-search-ui#10

Describe the solution you'd like

Provide a new method that allows you to pass in any link (with or without existing GET params), and have the appropriate analytics data attached to that link as additional GET params.

Ideally, allow for customisations of URL handling. EG: It would be really good if this mechanism could be used to change the analytics flow for developers who perhaps might like to use an internal route with redirects instead of the middleware.