Allow query arguments to be ignored for matching, and passed through

[fklein-lu]

A common use case for extra query arguments in URLs is Google Analytics data.

We should offer a filter that allows the whitelisting of a set of query arguments. These will be ignored for matching a redirect, but will be appended to the found redirect.

As an example, when _ga is whitelisted, http://example.com/article/?_ga=123 would be matched as http://example.com/article/, and the redirect would then be http://example.com/other-article/?_ga=123.

This enables tracking information to be relayed even when redirects are used.