created utility/Basic.cpp for methods that need not be inline
inserted #include "errors.h" forgotten in commit fe2a01ab
created former_MPI_Barrier macro
moved MPI_Allreduce calls from .h to .cpp
commented out unused declarations in MPIdata.h
changed "ipic run" to call mpirun rather than mpiexec
added number of threads to utility/MPIdata.cpp output
issue#62: changed getVelocityDistribution to make one MPI_Allreduce call (untested)
issue#35: replaced MPI_Barrier with former_MPI_Barrier; MPI_Barrier is no longer no-op
issue #63: made invalid_value_error thread safe
warning messages should issue warning and proceed, not exit
implemented MPIdata::exit(code) to exit after calling MPI_Finalize()
issue #64: MPI should be initialized immediately
issue #66: moving includes out of Collective.h
iss #65, iss #67: defined options for second-order accuracy
fixed compile errors on icpc probably introduced two commits ago
"ipic exec" now calls mpiexec, just as "ipic run" calls mpirun
removed unnecessary header includes in Grid3DCU.h (iss #66)
Merge branch 'merge2amaya' into vectorizing

Conflicts:
	include/Collective.h
	include/Grid3DCU.h
	inputoutput/Collective.cpp
	scripts/ipic.py
	utility/MPIdata.cpp