Use IME service logo or icon if exists.

With this CL, AvailableVirtualKeyboardFragment searches icon resource in
the following order, which makes it easier to find a certain IME when
one APK contains multiple IMEs.
 1. Service Logo
 2. Service Icon
 3. Application Logo
 4. Application Icon

Bug: 28204635
Change-Id: I406ccc0d53e6ec69793c2fc8be8c6c1c90b34811