move precursor boundary conditions to BoundaryConditions folder

...gpu/AtmosphericBoundaryLayer/AtmosphericBoundaryLayer.cpp

pythonbindings/src/gpu/submodules/boundary_conditions.cpp

src/gpu/core/BoundaryConditions/BoundaryConditionFactory.cpp

src/gpu/core/BoundaryConditions/BoundaryConditionFactory.h

src/gpu/core/BoundaryConditions/Precursor/Precursor.cu

src/gpu/core/BoundaryConditions/Precursor/Precursor.h

...re/BoundaryConditions/Precursor/PrecursorDistributions.cu

...itions/Precursor/PrecursorDistributionsSubgridDistance.cu

...core/BoundaryConditions/Precursor/PrecursorEquilibrium.cu

...onditions/Precursor/PrecursorNonReflectiveCompressible.cu

...pu/core/BoundaryConditions/Precursor/Precursor_Device.cuh

src/gpu/core/GPU/GPU_Interface.h

src/gpu/core/GPU/GPU_Kernels.cuh

src/gpu/core/GPU/LBMKernel.cu