CONFIG: adjustments to environment

- provide default WM_DIR if not already set, to improve robustness if a
  reduced environment is used

- add etc/ to WM_PROJECT_SITE search. This makes the site directory
  structure consistent with the OpenFOAM structure.
  Eg,

      WM_PROJECT_SITE/etc/..
      WM_PROJECT_SITE/bin/..
      WM_PROJECT_SITE/platforms/..

- Don't set/export WM_OSTYPE.  The default is POSIX and is properly
  defaulted throughout, including in CMakeLists-OpenFOAM.txt (also for
  Catalyst)

bin/foamEtcFile

@@ -310,7 +310,7 @@ case "$optMode" in (*u*) # (U)ser
 esac
 
 case "$optMode" in (*g*) # (G)roup == site
-    dirList="$dirList $groupDir/$projectVersion $groupDir"
+    dirList="$dirList $groupDir/$projectVersion/etc $groupDir/etc"
     ;;
 esac