Analysis - be able to expire client side cache

If an analysis grid was wrong, and cached client side, there's currently no way to force clients to retrieve the fixed version.

Before you load a node/grid you call node_load which returns the current version so you can build the URL. We can expire these node/version urls server-side by bumping settings.CACHE_VERSION but there is no way to tell the clients that their cache is out of date, except by say incrementing the versions.

If we had some kind of global and just tacked it onto the end of every URL eg ```?cache_version=42``` we could then force client to retrieve the data again.