Element picker

Mouse selection works.
Minor bug with keypress listening when Chrome console is up to be fixed later.

To run demo:

1) In CTS project, run `grunt web_server`
2) In CTS-UI project, run `grunt web_server`
3) Navigate to `http://localhost:8000/demo/picker.html` and follow the instructions in the alert box.

To view invocation:

Look at demo/pickerdemo.js