Support node references

I've set up an "image" CCK type. I have node reference fields on other content types that point to these image nodes, and I want to insert images from these other referenced nodes into the body of a node.

This patch adds additional styles for Insert widgets: node build modes and views that take a node ID argument. It has all kinds of little weird problems, so it's really presented for discussion and feedback.

What works:

1. I can refer to nodes and insert the rendered representations of them into the node body.
2. Any node reference widget can be used.

What doesn't work:

1. The insert behavior only works after the node reference field has been saved.
2. Multiple values and option and select widgets don't make any sense.

I'm posting this to Insert because it was relatively quick work to make Insert do this. However, this does break some of the fundamental concepts of Insert. Node references are not images or files, and Insert module assumes that we're working with files/images only. Styles can't be restricted to certain field types, so imagefield styles appear on node reference widget settings and vice versa.

Insert's javascript relies on a distinctive wrapper around the form element of the insertable item, and by default node reference widgets have no such wrapper. This patch adds this wrapper in a pretty clumsy way.

This may produce invalid HTML, too. If we can insert a full node into another node, the rendered node will need to be stashed in a hidden form element. Surely there are size limits to reckon with. If you enable many different insert styles for the widget, you're running views for each possibility, causing the node edit form to be very very heavy.

Why should the widget only support node IDs? I can pass a node ID value to a term ID views argument and handle all that with some custom argument validation.

Access and permissions are also problematic... the node or view is rendered using the current user's permissions. Users who are viewing the node where it's embedded in the body may not have permission to see that other node or view. If the user has "administer views" permission and the views admin links are enabled, these admin links are inserted into the node body as well. Probably this could be addressed with template preprocess functions on the views displays or by providing a views display plugin specifically for Insert style output.