Bug 963556: Update NFC Manager, Handover to use new shared nfc_utils.js.

Conflicts:
	apps/system/js/nfc_handover_manager.js
	apps/system/js/nfc_manager_utils.js
Bug 961800 - Implement Child Window Factory

Conflicts:
	apps/system/js/app_transition_controller.js
	apps/system/js/app_window.js
	apps/system/js/app_window_manager.js
	apps/system/js/cards_view.js
	apps/system/style/window.css
Merge pull request #17369 from yurenju/nfc

Bug 963556: Update NFC Manager, Handover to use new shared nfc_utils.js. r=@alivedise
Merge pull request #17370 from alivedise/bugzilla/961800_master_merging/child-window-factory

Bug 961800 - Implement Child Window Factory, r=etienne
Bug 971556 - [System2] Instantiable SourceView.