Made VF_GPU work with the "new" cmake

Changed the setting the compiler options to the new cmake function: target_compile_options

* feature/MergeMainGPU: (785 commits)
  Part 5.  Move original VF gpu into gpu/
  Part 4.  Move original VF gpu into gpu/
  Part 2.  Move original VF gpu into gpu/
  Part 2.  Move original VF gpu into gpu/
  Part 1.  Move original VF gpu into gpu/
  added two flags: 1. calcPlaneConc and 2. writeVeloASCIIfiles
  cleans up UpdateGrid27.cpp and Simulation.cpp
  fixes bug with pressure outflow boundary condition in redesign
  adds documentation to the buildGrids() method in the GridGenerator
  TODO Slip BC
  fixes some bugs for new updateGrid27 function, especially initialization of boundary condition coutners
  add DragLift and Cp calculation ... STILL NOT WORKING
  add calcMacroscopicQuantities ... STILL NOT WORKING
  fixed the "level-bug" in the two scaling function calls ... STILL NOT WORKING
  add a missing scaling version (found in simulation.cpp) .... STILL NOT WORKING
  add  fineToCoarse and coarseToFine ... STILL NOT WORKING
  fixed some stuff and changes preCollisionBC ... STILL NOT WORKING
  start of redesign for time loop - UpdateGrid27 splitted into multiple functions - WORK IN PROGRESS
  fixes "Aileens bug" with edges between periodic and BC side of the domain
  enables LBM and GKS in CMakeLists
  ...

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#	CMakeLists.txt

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Merge pull request 'Added missing header for usleep for apple systems: https://developer.apple.com/library/archive/documentation/System/Conceptual/ManPages_iPhoneOS/man3/usleep.3.html' (#2) from peters/VirtualFluids:feature/suresoft into develop