[6.x] Publish container tweaks

[jasonvarga]

A few small changes to the publish container, primarily in support of the collaboration addon's multisite handling:

• The publish-container-created event emits reference and site as refs, so consumers can observe them as they change (e.g. when the user switches localizations).
• The entry, global, and term publish forms now update reference when switching localizations, so the container's reference stays in sync with the active item.
• pushComponent removes the component from the container's components array when its destroy() is called, so pushed components can clean themselves up.
• The Components renderer keys by component.id instead of component.name, allowing multiple components of the same type to coexist.