Moved all globals into a model object.
Update text placeholders to spans.
Merge remote-tracking branch 'origin/lucyhe-polymer_ui_for_copypaste' into lucyhe-add_arabic_translation

Conflicts:
	src/samples/copypaste-socks-chromeapp/getter.html
	src/samples/copypaste-socks-chromeapp/getter.ts
	src/samples/copypaste-socks-chromeapp/giver.html
	src/samples/copypaste-socks-chromeapp/giver.ts
	src/samples/copypaste-socks-chromeapp/root.ts