improves cuda kernel for acoustic simulations; adds file assemble_MPI_scalar_cuda.cu and assemble_MPI_vector_cuda.cu
updates configuration files to compile CUDA executables without MPI
adds depedency for locate_receivers.f90 compilation
Merge branches 'master' and 'devel' of https://github.com/geodynamics/specfem3d into devel
adds flop count to compute_forces_viscoelastic_Dev_5p() routine
removes header files from repository which are created automatically by scotch compilation
performance optimization for acoustic & elastic CUDA kernels
merges with upstream/devel
updates configuration files and m4/ version for CUDA compilation
updates meshing to be able to use tomographic models with Par_file setting (MODEL = tomo); fixes geocubit scripts to be able to use python-scripts within CUBIT; updates unit testing which can be run by: make tests; moves module tomography_par into file model_tomography.f90; updates use-statements
removes trailing spaces