Merge branch 'feature/remove_old_readme' into develop

* feature/remove_old_readme:
  Remove old readme.

readme_gpu.md

-Software Requirements:
-======================
-
-CMake [cmake.org](https://cmake.org/):
-* minimum version 3.13
-
-CUDA [developer.nvidia.com/cuda-zone](https://developer.nvidia.com/cuda-zone):
-* Minimum CUDA Version 9.0
-* Minimum Compute Capability 3.0, because of maximal number of Blocks in x direction
-* Recommended Compute Capability 6.0, because of atomics for double precision floating point data (GKS only)
-    
-Paraview [www.paraview.org](https://www.paraview.org/):
-* any version, for example the most recent
-    
-C++ Compiler:
-* with C++11 support, for example gcc6.3 or Visual C++ 14.0
-    
-How to get VirtualFluidsGPU:
-==========================
-
-Option 1: use git
-1. checkout out https://git.irmb.bau.tu-bs.de/VirtualFluids/VirtualFluidsGPU.git with your credentials
-
-Option 2: without git
-1. go to git.irmb.tu-bs.de
-2. Log in with your credentials
-3. click on VirtualFluids/VirtualFluidsGPU
-4. click on the download symbol on the top right and download zip/tar.gz file
-
-How to build VirtualFluidsGPU:
-============================
-
-1. CMake the project
-2. set the output path in targets/apps/LidDrivenCavity/LidDrivenCavity.cpp
-3. build the project ("compile")
-4. run the generated executable (usually in <build directory>/bin/)
-
-Known Issues:
--------------
-
-If CMake does not find CUDA_CUT_INCLUDE_DIR use and set the correct CUDA Pathes in CMakeLists.txt in the base directory in lines 35, 36.
-
-VirtualFluidsGPU results files:
-===============================
-
-VirtualFluidsGPU generates a the time series of output files directly in the output path. In Paraview these time series can be read directly.
-
-VirtualFluidsGPU change between Double and Single Precision:
-============================================================
-
-Option 1:
-1. go to CMakeLists.txt in the base directory
-2. go to line 83 to switch ON/OFF VF_DOUBLE_ACCURACY
-
-Option 2:
-Check/uncheck the item VF_DOUBLE_ACCURACY in CMake.
-
-Documentation:
-==============
-
-The doxygen generated documentation can be found [here](https://git.irmb.bau.tu-bs.de/doku/GPU).
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