Fix account selector UI in Contact editor.

1) Hide the "Saving to" account container when there're both
read-only and writable contacts.
2) Add more space between name field and whatever are above it.
3) Show linked contacts selector when there's only one read-only.

BUG 25219324

Change-Id: I9229132a833400de5cb542bc5363a4e3f36c9d1a