Add start of appengine package.
Add start of appengine package.

This is a subset of the existing appengine package;
we will rebuild it gradually.

Change-Id: I8b2f8e70e2d4a4681e921ecf724cb0636e3ab212

mzimmerman/appengine,fuchsia-mirror/third_party-github.com-golang-appengine,mzimmerman/appengine,skyeunknown084/appengine,skyeunknown084/appengine,fuchsia-mirror/third_party-github.com-golang-appengine,golang/appengine,flowlo/appengine,flowlo/appengine,flowlo/appengine,golang/appengine,skyeunknown084/appengine,mzimmerman/appengine