Changes introduced in this commit are the following:

- CUDA streams: Add support for asynchronous (un)packing operations using CUDA
  streams in cuda::communication::GPUPackInfo. Through asynchronous operations
  it is possible to overlap GPU computation and MPI communication in simulations
  (e.g. LBM simulations). Asynchronous copies in CUDA require pinned memory on
  the host, and for that purpose a staging buffer is introduced (i.e.
  cuda::communication::PinnedMemoryBuffer) in the cuda module, which is used to
  stage data between the GPU and the MPI buffers.

- zyxf layout: Add zyxf field layout support in GPUPackInfo through extensions
  of the functions in cuda::GPUCopy.

- Extended GPUPackInfo test: Add stream and zyxf layout tests to the
  GPUPackInfoTest to test the proposed implementation.

- Extended Kernel: add CUDA stream and shared memory configuration support in
  cuda::Kernel class.

Signed-off-by: João Victor Tozatti Risso <joaovictortr@protonmail.com>

Resolve "PE Union should conserve momentum upon creation"

Closes #43

See merge request walberla/walberla!66

Improved iterative collision detection with GJK-EPA

See merge request walberla/walberla!62

searches for #pragma once in every .h file

fixed missing semicolon in Likwid macro

See merge request walberla/walberla!65

OpenMPI 3.0 support

See merge request walberla/walberla!64

OpenMPI 3.0 by default does not allow running with more processes than CPUs

Resolve "No regex_replace in GCC 4.8"

Closes #38

See merge request walberla/walberla!58

New field utilities

See merge request !61

Resolve "Suppress undefined behaviour warning in Send/Recv Buffer"

Closes #39

See merge request !59

New pe coupling functionalities

See merge request !56