- basis of generic properties editor works!
 * a few workarounds still needed because of the lack of "template repeat"
to iterate over object properties in polymer
 * added type detection methods so that correct ui elements (text editor for
strings, number input for numeric properties) can be displayed
 * added sub elements for the different types (text, number)
 * when the values change, the currently selected object's attributeChange
method is called (a bit of a hack really, but it works), and updates the
objects accordingly