Update core elements

Updated the core elements and migrated the example for core-signals.

Marked as a breaking change because of a change in the core-animation customEffect callback signature (also updated the example to adjust for this).

A lot of other junk is included here because of the bower update, let me know if I should be not including some of it (specifically all the test related junk). However if I don't include it then any time somebody runs bower update its going to do this to them.... so I'm inclined to keep it around. Another option might be adding some things to .gitignore?
let's update our sample with this change too.

Same thing with the demo.html files below...