Skip full node_load() in formatter

The nodereference module's formatters currently do a full node_load() on the target node, and create a link with l(). It then, conditionally, UNlinks that string with strip_tags(). Both of those are horribly inefficient, especially when using a nodereference field in a View. It can mean easily a half-dozen extra, needless queries for each record being listed.

The attached patch does two things to formatter function. First, it skips the node_load() in favor of a static-cached simple query against the node table. I've never seen a module modify a node title on load instead of on save (and if it did, it would be ignored in various places in core already), so the node_load() is not needed. It then builds the link only if necessary. Secondly, it introduces a 3rd formatter "nid only", which does no lookup at all. That is useful in a View (or simple node view) where you want to load the node reference field as a nid, for whatever reason, but won't be displaying it to the user. Getting the node's title is, therefore, a waste of time.

With this patch, I was able to cut the number of queries on a single page in half from ~150 to ~75, without breaking any other functionality. Sounds like a win. :-)