Attempts to load an image file from 'filename', using the provider identified by 'type'.
static CL_PixelBuffer CL_ImageProviderFactory::try_load( const CL_String & filename, const CL_String & type = CL_String (), CL_VirtualDirectory directory = CL_VirtualDirectory (), CL_String * out_failure_reason = 0);
Detailed description:
If the type is an empty string, it uses the extension of the filename to determine what type it is.
The virtual directory will be used as a the source.