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.csh/compiler

@@ -31,7 +31,6 @@
 #------------------------------------------------------------------------------
 
 switch ("$WM_COMPILER_TYPE")
-case OpenFOAM:
 case ThirdParty:
     # Default versions of GMP, MPFR and MPC, override as necessary
     set gmp_version=gmp-system
@@ -90,21 +89,6 @@ Please check your settings
 UNKNOWN_COMPILER
         breaksw
     endsw
-
-    setenv WM_COMPILER_TYPE ThirdParty  # Canonical name
-    breaksw
-endsw
-
-# Common settings (system or ThirdParty)
-switch ("$WM_COMPILER")
-case Clang*:
-    # Using clang - not gcc
-    setenv WM_CC 'clang'
-    setenv WM_CXX 'clang++'
-    breaksw
-case Icc*:
-    setenv WM_CC 'icc'
-    setenv WM_CXX 'icpc'
     breaksw
 endsw