fixed parts rescaling

Fixes incorrect rescaling of parts, containing "scale" in MODEL
description. For example, many of KW Rocketry parts
[URL="http://forum.kerbalspaceprogram.com/threads/51037-0-24-2-KW-Rocketry-v2-6c-Available-New-5m-Parts!-24-07-2014"][/URL]
or Cubic Trusses from Spherical and Toroidal Tank Pack by
Talisar[URL="http://forum.kerbalspaceprogram.com/threads/30673-0-23-5-Spherical-and-Toroidal-Tank-Pack-%28Updated-05-02-14%29-%28New-download-link%29"][/URL]