CONFIG: improve prefix matching for system libraries (#1607)

- missed detection of system libraries when installed with multiarch
  paths like /usr/lib/x86_64-linux-gnu

CONFIG: improve handling of group/user config files (#928)

- changed bashrc handling of FOAM_CONFIG_NOUSER to use
  FOAM_CONFIG_MODE instead. Propagate into foamEtcFile to make this
  a stickier control.

  This change allows better control, but also enables cluster
  installations to define their own value within the OpenFOAM prefs.sh
  file to prevent users accidentally mis-configuring things if
  necessary.

- remove undocumented handling of an (a)ll mode in foamEtcFile to
  avoid potential pitfalls.

- add support for FOAM_CONFIG_ETC handling.
  This allows injection of an extra search layer when finding
  project etc files

ENH: improvements to foamConfigurePaths (#928)

- handle FOAM_CONFIG_ETC implicitly, or explicitly with the new
  -etc option.

STYLE: more explicit wording in foamConfigurePaths usage (#1602)

- document that an absolute path (eg, -scotch-path) overrides/ignores
  the equivalent ThirdParty setting (eg, -scotch)

- longer options -system-compiler and -third-compiler for -system
  and -third, respectively. Clearer as to their purpose.

- adjust the location sanity check to look for META-INFO directory.

src/OpenFOAM/global/fileOperations/collatedFileOperation/collatedFileOperation.C

@@ -286,7 +286,7 @@ Foam::fileOperations::collatedFileOperation::collatedFileOperation
                    "enabled, deactivate" << nl
                 << "         threading by setting maxThreadFileBufferSize "
                     "to 0 in" << nl
-                << "         $FOAM_ETC/controlDict"
+                << "         OpenFOAM etc/controlDict"
                 << endl;
         }