This CL is mostly a renaming s/json/serial/, abstracting the
oracle package away from any particular data syntax. (The
encoding/* machinery is very clean; clearly I should have
structured it this way from the outset.)
Supporting XML then becomes a one-liner in cmd/oracle/main.go.
Also: call MarshalIndent(), not Marshall() then Indent().
R=crawshaw
CC=golang-dev
https://golang.org/cl/13858046
