Use auto build version info for embedding version information

This is better, integrates with git, gives us more detail, and I don't
have to explicitly pass it around everywhere.

resource/session.go

@@ -116,9 +116,3 @@ func (res *sessionR) Get(ctx context.Context, r *http.Request, user platform.Use
 		},
 	}, nil
 }
-
-var version string = "unknown"
-
-func SetVersion(v string) {
-	version = v
-}