Add OpenSHMEM alloc/free wrapper functions
Initialize OpenSHMEM on file open
OpenSHMEM-based collective write function

Initial implementation of MPI+OpenSHMEM-based collective write function.
Add .o files to gitignore
Remove rank<->pe mapping

MPI rank and OpenSHMEM PE are always equal in MVAPICH2-x.
Remove debugging print statement
Remove openshmem stuff
Replace openshmem implementation with MPI rma