Replace or remove import "appengine/foo" examples

[vdepabk2t]

https://github.com/golang/appengine says:

If you're currently using the bare appengine packages (that is, not these ones, imported via google.golang.org/appengine), then you can use the aefix tool to help automate an upgrade to these packages.

The import paths for App Engine packages are now fully qualified, based at google.golang.org/appengine. You will need to update your code to use import paths starting with that; for instance, code importing appengine/datastore will now need to import google.golang.org/appengine/datastore.

If there are still good examples of "bare packages," please use them instead, replacing the ones here. (I don't know of any, but I'm still a Go newbie.) If there aren't, please remove these.