This creates the skeleton of an AppEngine app for perfdata.golang.org
and adds an initial implementation of /upload that saves the provided
file into Cloud Storage.

Change-Id: I1fe19b27841ab62aad146d1d1019996634012d35
Reviewed-on: https://go-review.googlesource.com/34620Reviewed-by: Russ Cox <rsc@golang.org>