message: ENH: update Axom version to v0.3.1
diff: ## otherwise, the hard-coded values will go in to the config.
  set(AXOM_VERSION_MAJOR 0)
  set(AXOM_VERSION_MINOR 3)
  -set(AXOM_VERSION_PATCH 0)
  +set(AXOM_VERSION_PATCH 1)
  string(CONCAT AXOM_VERSION_FULL
  "v${AXOM_VERSION_MAJOR}"
  ".${AXOM_VERSION_MINOR}"
  