attribute editors

The Sites 12c documentation has some instructions and examples of setting up a custom attribute editor, but they don't get very complicated. I wanted to add some functionality to the built in editor for picking an asset and realized there are a lot of steps so blogging about it might be usefull for others. Building UI enchancements can feel like putting together a puzzle for the first time. This won't show a full working example but I'll point out all the files and key things that had to be done to add a button next to each selected attribute whether or not the attribute is set to single...