web interfaces: don't include version number in html, only return it after authentication

second round for issue #322

webaccount/account.go

@@ -17,6 +17,7 @@ import (
 	"net/url"
 	"os"
 	"path/filepath"
+	"runtime"
 	"strings"
 	"time"
 
@@ -368,6 +369,11 @@ func (w Account) Logout(ctx context.Context) {
 	xcheckf(ctx, err, "logout")
 }
 
+// Version returns the version, goos and goarch.
+func (Account) Version(ctx context.Context) (version, goos, goarch string) {
+	return moxvar.Version, runtime.GOOS, runtime.GOARCH
+}
+
 // SetPassword saves a new password for the account, invalidating the previous
 // password.
 //