core-localstorage, core-selector, and core-selection tests

This PR contains all remaining tests to port from https://github.com/Polymer/core-tests
(they are not many)

Not all tests are working yet
see commit messages for more details

related to #41 

I try to come up with some additional tests.
I think we can make this work temporarily by doing:
`var detail = new JsObject.fromBrowserObject(event)['detail'];`