Futureproof trusted credentials for multiple profiles

Made use of the shiny LayoutTransition.CHANGING animations. Now it's a
little more obvious where things are going when tapping a header.

Future work: maybe show the usernames / user icons in there too? This
could get complicated, and it'll need to be done everywhere at once.

Change-Id: Id7396235abe6218d591d16db91af0f56a83a7bcd
Fix: 28310002