use site methods instead of family methods

- remove BaseSite.linktrail() which is already derived from
  Family.linktrail(code) by BaseSite.__getattr__()
- port the doc string to the corresponding family method
- remove BaseSite.nice_get_address() which is already derived from
  Family.nice_get_address(code) by BaseSite.__getattr__()
- use methods version(), protocol(), hostname()

Change-Id: I33c9e6db6c2797bb7e637f3c46cb8af7f08037b8
Merge "use site methods instead of family methods"