Swtich to model where BuildingBlocks do not know their parents

src/MRIBuilder.jl

src/building_blocks.jl

src/concrete_blocks.jl

src/containers/containers.jl

src/containers/sequences.jl

src/global_model.jl

src/gradients/gradients.jl

src/gradients/instant_gradients.jl

src/gradients/integrate_gradients.jl

src/gradients/pulsed_gradients.jl

src/inserted_building_blocks.jl

src/pulses/constant_pulses.jl

src/pulses/instant_pulses.jl

src/pulses/properties.jl

src/pulses/pulses.jl

src/pulses/sinc_pulses.jl

src/readouts/instant_readouts.jl

src/variables.jl

src/wait.jl