Add ability to change hashed query strings even in a second pass

This may be a nice addition if you feel like it belongs to this plugin.
I'm using this plugin with a manifest that has query string parameters with the hashes, instead of file renames. I've found it useful to add the ability to override an existing query string parameter, so I don't have to keep a different source and destination for my cache-busted files.
This is similar to how other plugins work (like https://www.npmjs.org/package/gulp-rev-append). But I like gulp-fingerprint because is manifest-driven so it doesn't require to explicitly mark the urls I want to cache bust.
I've added a new test which hopefully shows what's the intended use.