First pass of load files through an interface (to allow loading from memory, zip file etc). So instead of posix fopen/fread, using CommonFileIOInterface.

A fileIO plugin can override custom file IO operations. As a small test, load files from a zipfile in memory.
Default fileIO implementation is in examples/Utils/b3BulletDefaultFileIO.h
Affects URDF, SDF, MJCF, Wavefront OBJ, STL, DAE, images.

examples/Importers/ImportColladaDemo/LoadMeshFromCollada.h

@@ -28,7 +28,8 @@ void LoadMeshFromCollada(const char* relativeFileName,
 						 btAlignedObjectArray<ColladaGraphicsInstance>& visualShapeInstances,
 						 btTransform& upAxisTrans,
 						 float& unitMeterScaling,
-						 int clientUpAxis);
+						 int clientUpAxis,
+						 struct CommonFileIOInterface* fileIO);
 
 //#define COMPARE_WITH_ASSIMP
 #ifdef COMPARE_WITH_ASSIMP