Enable the Golang client library to create the new text formats.

Most important here is the simple & flat text format, but while I'm on
it, I have also added the text representations for protobufs (which is
purely meant for debugging purposes). I hope my basic idea about
handling those various protocols (and the text package) becomes
clearer now.

Change-Id: I7299853eadc82a426101e907f2b3d4e37f9e4c71