profile details fragment: move setup from onCreate to onActivityCreated

this is what the docs suggest and it fixes a problem with the toolbar
title changing to from profile name to 'Profile details' when the screen
is rotated. This is because the title is set during the setup and onCreate
isn't necessarily run when the screen is rotated (contrary to
onActivityCreated which is re-run since the activity is re-created on
reconfiguration (of which screen rotation is an instance))