update/add examples and tests

add paper-dialog-base and cherrypick https://github.com/Polymer/paper-shadow/pull/25 for setZ method on paper-shadow

update config with a few new elements and rerun

remove webcomponentsjs

bower update and generate wrappers

BUG= https://github.com/dart-lang/paper-elements/issues/64
R=sigmund@google.com

Review URL: https://codereview.chromium.org//774143004