Add get_non_tof_ProjData to ProjData

This is more of a discussion point than an issue. That was first mentioned here: #1321 #1320 (comment) w.r.t accessing non-TOF sinograms/viewgrams from TOF data without having to load each TOF sinogram/viewgram into python.

However, this should be generalized. It might be useful to add this conversion from TOF ProjData to non-TOF ProjData in the Projdata class.

Alternatively, it could be implemented into SSRB. But SSRB does not currently support TOF compression.

STIR/src/buildblock/SSRB.cxx

Lines 44 to 55 in 151c457

    
           ProjDataInfo * 
        
           SSRB(const ProjDataInfo& in_proj_data_info, 
        
                const int num_segments_to_combine, 
        
                const int num_views_to_combine, 
        
                const int num_tang_poss_to_trim, 
        
                const int max_in_segment_num_to_process_argument, 
        
                const int num_tof_bins_to_combine 
        
                ) 
        
           { 
        
             if (num_tof_bins_to_combine!=1) 
        
               error("SSRB: num_tof_bins_to_combine (%d) currently needs to be 1", 
        
                     num_tof_bins_to_combine);

@KrisThielemans @NikEfth @NicoleJurjew thoughts?

	ProjDataInfo *
	SSRB(const ProjDataInfo& in_proj_data_info,
	const int num_segments_to_combine,
	const int num_views_to_combine,
	const int num_tang_poss_to_trim,
	const int max_in_segment_num_to_process_argument,
	const int num_tof_bins_to_combine
	)
	{
	if (num_tof_bins_to_combine!=1)
	error("SSRB: num_tof_bins_to_combine (%d) currently needs to be 1",
	num_tof_bins_to_combine);