use DOM fragments instead of always creating elements

[jasongrout]

Taking a tip from William, it may be marginally faster and (more importantly) separates content/presentation better to use DOM fragments and cloning rather than creating elements (for example, for interact controls, or anywhere else we use the "ce" function). See http://ejohn.org/blog/dom-documentfragments/
For example (as a tip from William), load a lot of hidden divs/spans that contain DOM fragments for each interact control, etc. Clone these as needed and insert them into the DOM where needed.