Refactor sinogram

Some changes to simplify the sinogram in sequences.

This includes some clean up around the scan_info.

• add_metadata was reworked to remove the use of _inpars.scan_info
• _inpars.scan_info was completly removed
• TomoSinogram is now created only when it is needed
• TomoSinogram is now linked to a specific ROI name
• half_acquisition does not generate extra metadata, it's already the default one
• update_tomo_scan_info was created to update the doct instead of creating a new one

There is still small inconsistent stuffs (like a code creating a default ROI, which is never called if there is no ROIs).

But now we could think of the policy to configure a sinogram by default.