Add support to use goole-apis element in a dynamic SPA

[lcaggio]

Adding support to use the google-apis element in a Single Page Application, at the moment when the element is dynamically added in the the page, it does not load the library.

Example: When a google-client-loader is loaded in a dom-repeat template element, it do not load the library because when the dom-repeat template is stamped, client libraries are already loaded, but the name and version are not bound, so the library does not get loaded.