ENH: add wmUNSET alias to source etc/unset.{csh,sh}

- renamed clearEnv -> unset

etc/aliases.csh

@@ -22,7 +22,7 @@
 #     along with OpenFOAM.  If not, see <http://www.gnu.org/licenses/>.
 #
 # File
-#     aliases.csh
+#     etc/aliases.csh
 #
 # Description
 #     Aliases for working with OpenFOAM
@@ -38,6 +38,9 @@ alias wm32 'wmSET WM_ARCH_OPTION=32'
 alias wmSP 'wmSET WM_PRECISION_OPTION=SP'
 alias wmDP 'wmSET WM_PRECISION_OPTION=DP'
 
+# clear env
+alias wmUNSET='source $WM_PROJECT_DIR/etc/unset.csh'
+
 # Toggle wmakeScheduler on/off
 #  - also need to set WM_HOSTS
 # ~~~~~~~~~~~~~~~~~~~~~~~~~~~~