Reporting of phantom spatial sampling in obj.info structure.

[curtcorum]

Feature Request

Based on discussion from #319 and #311 issues can arise due to artifacts of Cartesian sampling on phantom and (especially) Cartesian sampling of spoiled steady state gradient echo sequences.

Providing information about the spatial resolution of the phantom can help users to choose simulation parameters that can avoid artifacts.

...we could have a dictionary where we can put relevant information for the phantom (obj.info similar to seq.DEF). Those parameters in obj.info should be optional, and not be necessarily defined in every phantom. For example, if the sampling is not cartesian the resolution variable could not make sense.