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.

etc/templates/closedVolume/README

@@ -11,7 +11,7 @@ Overview
 Meshing
 =======
 + Meshing is setup as in the inflowOutflow template
-+ See $FOAM_ETC/templates/inflowOutflow/README for details
++ See etc/templates/inflowOutflow/README for details
 + The setup includes an example for one named patch to be generated in the mesh
 + In snappyHexMeshDict, replace <CADregionName> with the name of region in the
   trisurface; replace <patchName> with the name of the resulting mesh patch
@@ -21,4 +21,4 @@ Initialisation
 + In the field files in the 0 directory, set initial values
 + The template includes a fixedValue boundary condition on <patchName> in 0/T
 + The user can replace <patchName> with a real mesh patch name and apply a
-  fixed temperature on that patch
+  fixed temperature on that patch