added cudaHostAllocator for pinned vectors
minor
use one stream (non-null)
running on one stream, device sync
async buggy at the time (sync problem?)
downloading into two different arrays

Ghosts for the next subdomain need to be extracted and store additionally
added streams to GPUTimer
fixed typo
2 streams with 2 host buffers overlap
minor
minor
stripped h2d_3DArray Z size to actual fit, added processing counter
added sim destruction to main.cpp and in destructor of Test_SteadyState