Google App Engine SDKs 1.9.4

Upgrades App Engine SDKs to 1.9.4 across Java, Python, Go 32/64.
SHAs verified from Google's download site at https://developers.google.com/appengine/downloads
google-app-engine: add 1.9.4 bottle.
go-app-engine-64: add 1.9.4 bottle.
go-app-engine-32: add 1.9.4 bottle.
app-engine-java-sdk: add 1.9.4 bottle.