Customizer submit (activate/publish) flow
|Reported by:||jane||Owned by:||koopersmith|
When someone submits their changes through the customizer, they should be returned to the managed themes screen.
For modifications to the current theme, show yellow alert:
"Your theme customizations have been published."
For new theme activation, show the message we already show the next time the themes screen is loaded. "New theme activated. [widget prompt if applicable]"