Various changes to optimizeTextures

Fixed Multithreading, fixed a bug with alpha channels and changed the output format to tga.

Texturing/OptimizeTextures/freeze_support.py

@@ -0,0 +1,6 @@
+import multiprocessing
+import sys
+
+if getattr(sys, 'frozen', False):
+    # Running as a frozen executable
+    multiprocessing.freeze_support()