get handler: still set content-type text/plain when it's a small all-utf-8 blob (for JSON metadata)

Change-Id: I8a55bb44199c015515ea3aa46f912d8d5a472a5c
appengine: remove all the symlinks.

No longer necessary as of Go App Engine SDK 1.7.4.

Change-Id: Ie724d31ce73fe034c4039dc9068077750b7175a5
App Engine: compiles and kinda starts again; doesn't work.

With SDK 1.7.4.

Change-Id: Ide16c990fc139e7f450cea508c74f13ed79aac21