Merge branch 'release'

* release:
  fix: only delete array if it was allocated
  Fix Circle CI to use the correct _ROOT variables
  Change EVPATH -> EVPath in CMake for consistency and best practices
  Cleanup SST's CMake
  Remove spurrious use of mpi.h
  Make SST dependent on MPI for now
  Allow SST examples to work with and without MPI
  Consistently use the PackageName_ROOT CMake variable