add btFileUtils::toLower to convert a string (char*) to lower case

URDF import demo: add COLLADA .dae file support
add FiniteElementMethod demo, extracted from the OpenTissue library (under the zlib license)
don't crash if loading an invalid STL file
add comparison with Assimp for COLLADA file loading (disabled by default, to avoid library dependency)
Gwen: disable some flags that make the build incompatible

Demos3/FiniteElementMethod/OpenTissue/utility/utility_greater_ptr.h

@@ -0,0 +1,33 @@
+#ifndef	OPENTISSUE_UTILITY_UTILITY_GREATER_PTR_H
+#define	OPENTISSUE_UTILITY_UTILITY_GREATER_PTR_H
+//
+// OpenTissue, A toolbox for physical based	simulation and animation.
+// Copyright (C) 2007 Department of	Computer Science, University of	Copenhagen
+//
+#include <OpenTissue/configuration.h>
+
+#include <functional>
+
+namespace OpenTissue
+{
+  namespace utility
+  {
+
+    /**
+    * Greater Than Test.
+    * This is used for doing a greater than test on data
+    * structures containing pointers to data and not instances.
+    */
+    template<class T>
+    struct greater_ptr 
+      : public std::binary_function<T, T, bool>
+    {
+      bool operator()(const T& x, const T& y) const { return (*x)>(*y); }
+    };
+
+  } //End of namespace utility
+
+} //End of namespace OpenTissue
+
+// OPENTISSUE_UTILITY_UTILITY_GREATER_PTR_H
+#endif