First CMake release

[sanguinariojoe]

Welcome to 2001! :-)

Not much to say... I created a CMake compilation system, which is basically emulating your Makefile. There are some features pending (like Doxygen doc generation), but I would say is a good starting point

I tested it a bit, but more testing is obviously welcomed! You can do that typing:

git clone https://github.com/sanguinariojoe/gpusph -b cmake
# Build in a separate folder... Yes, a CMake superpower!
mkdir gpusph.build
cd gpuphs.build
ccmake ../gpusph/

The important variables are GPUSPH_PROBLEM, GPUSPH_USE_MPI, GPUSPH_USE_HDF5 and GPUSPH_USE_CHRONO