Make language change work more than once

g_permission_get_can_acquire returns FALSE if the permission has
already been obtained.
https://bugzilla.gnome.org/show_bug.cgi?id=701955
goa: Add separators to the list

This brings the page closer to the design.
goa: Don't hide explanation

It makes more sense to keep the explanation visible even
when the list is nonempty.
goa: sync add account dialog from control-center

We were missing the separators, among other things.
goa: Don't use trashcan icon

list-remove-symbolic is a bit less prominent.
Revert "goa: sync add account dialog from control-center"

This reverts commit 8d33e84814304b21c1741388b39f6d512e11aa22.
build: fix srcdir != builddir