Fixes / improvements in soft body:

avoid blow-up due to improper mass calculation for fixed nodes (happened when using clusters)
allow to create collision clusters for each tetrahedron or triangle, when using btSoftBody::generateClusters(0)
tweak soft body demos a bit, only draw debug wireframe if necessary

Demos/AllBulletDemos/Main.cpp

@@ -135,7 +135,7 @@ void	NextScene()
                  gDebugConstraints=1;
         }
 
-	if(testSelection>23)
+	if(testSelection>28)
 		testSelection=0;
 	if (glui)
 		glui->sync_live();