Add stick to position functionality to nodequeue + some general improvements

Hi,

There was a need in our company to stick the node in the queue to specific position. For example some story should always be on top and not get shifted when you add new item to the queue.

I created a patch to support this functionality. While I was working on it, I made some addition changes, for example when you reorder the queue and the save it we now have just one INSERT query regardless of the number of items in the queue.

Basically the main idea is that you can have multiple sticky nodes in the queue and all new items will be added to non-sticky positions (skip sticky item
and shift other non sticky items).
This functionality makes sense only when you add items on top of the queue (reverse in admin view), so maybe later I can add it only when reverse in admin view is selected.
I will also attach some screenshots to visualize 'stick to position' functionality.

The patch was tested by me and Adding, Saving, Shuffle, Reverse functionality is working properly. I think this functionality could be very useful for publishing websites like us, where editors create and mange queues of content.

Will appreciate any feed back on this.

Thanks