ENH: minor improvements to environment

- handle sourcing bashrc with a relative path (issue #383)
- handle sourcing from bash and zsh.
  Still need manual intervention when sourcing dash, sh, or ksh.
- replace grep in etc/cshrc with sed only
- logical instead of physical path for WM_PROJECT_DIR (issue #431).
  Doesn't seem to be possible for csh/tcsh.

  * Continue using physical locations when comparing directories,
    but not for the top-level FOAM_INST_DIR, WM_PROJECT_DIR.

- relocate WM_CC, WM_CXX overrides from etc/config.*/compiler
  to etc/config.*/settings to ensure that they are left untouched
  when etc/config.sh/compiler is sourced while making third-party
  packages (eg, gcc, llvm, CGAL).

- provide fallback FOAM_TUTORIALS setting in RunFunctions

STYLE: remove "~OpenFOAM" fallback as being too rare, non-obvious

etc/config.sh/functions

@@ -30,12 +30,12 @@
 #
 #------------------------------------------------------------------------------
 
-if [ -z "$WM_BASH_FUNCTIONS" ]
+if [ -z "$WM_SHELL_FUNCTIONS" ]
 then
     # Not previously loaded/defined - define now
 
     # Temporary environment variable to track loading/unloading of functions
-    WM_BASH_FUNCTIONS=loaded
+    WM_SHELL_FUNCTIONS=loaded
 
     # Prefix to PATH
     _foamAddPath()
@@ -69,7 +69,6 @@ then
     # Evaluate command-line parameters
     _foamEval()
     {
-        local file
         while [ $# -gt 0 ]
         do
             case "$1" in
@@ -105,7 +104,7 @@ then
 else
     # Was previously loaded/defined - now unset
 
-    unset WM_BASH_FUNCTIONS
+    unset WM_SHELL_FUNCTIONS
     unset -f _foamAddPath _foamAddLib _foamAddMan
     unset -f _foamEtc _foamEval