Merge branch 'feature/update_readme' into develop

* feature/update_readme:
  Extend the output part. Chang gpu and cpu to upper cases.
  Remove redundant -DNOMINMAX definition. Adds syscall include on unix systems.
  Set BUILD_VF_CPU default state to off.
  Fix typos.
  Change the default output path in the gpu app to <build>/bin/output according to the cpu app. Adds authors and contributing file. Clean up the readme file. Set the minimum cmake version to 3.13 according to the readme entry. Set the options BUILD_VF_CPU, BUILD_VF_GPU and BUILD_VF_UNIT_TEST to OFF by default.
  Adapt top level cmake list.

# Conflicts:
#	CMakeLists.txt
#	apps/gpu/LidDrivenCavity/LidDrivenCavity.cpp
#	src/basics/basics/utilities/UbSystem.h