Migrate to 6.2 UI

Issues present on 6.2.x:

• The component's dialog is broken. It doesn't store the slot/tag reference properly. After choosing a tag and saving the component doesn't show anything. It complains about not finding the node reference.
• The content app's detail subapp is broken. The action "Edit creative" throws an exception:

info.magnolia.campaign.manager.app.detail.CampaignEditorStatus.getPlatFormType()Linfo/magnolia/ui/vaadin/editor/gwt/shared/PlatformType;
RpcInvocationException: Unable to invoke method itemClick in com.vaadin.shared.ui.grid.GridServerRpc
caused by InvocationTargetException
caused by MethodException: Invocation of method itemClick in info.magnolia.ui.contentapp.browser.GridWithShortcuts$MouseShortcutsRegistrator$$Lambda$2083/324283533 failed.
caused by NoSuchMethodError: 

What already works:

• The content app's browser subapp. Including campaign schedules.
• The content app's tags subapp
• The content app's calendar subapp.
• The preview as visitor according to different campaigns (with components already configured in previous versions)