Merge branch 'develop-pre-release' of develop.openfoam.com:Development/OpenFOAM-plus into develop-pre-release

- the backend script should not be accessible from the PATH.
  Using deprecated/ adds a level of documentation.

- functionObjectLibs -> libs
- redirectType -> name
- change deprecated writeCompression flags types to Switch.

- cleanup some trailing ';;' from some dictionaries

STYLE: separate areaNormal/unitNormal method for primitives (issue #885)

See merge request OpenFOAM-plus!208

- regularise referencing of OpenFOAM env variables, sources etc.

- The problem is not 100% reproducible, but be somewhat conservative
  and now only close(stdin) for pure background (daemon-like) use of
  Foam::system(), where it can be useful.

  Using Foam::system() for launching background processes is currently
  only used for the doc browser.

- since 1612, FOAM_INST_DIR and foamInstDir longer have any
  special meanings when sourcing the bashrc or cshrc files.
  Thus no need for special treatment in any of the dispatch wrappers.

  Retained FOAM_INST_DIR as (unexported) variable in etc/bashrc,
  just in case people are using patched versions of etc/bashrc
  as part of their installation.

ENH: relax prefix restrictions on foamCreateVideo (issue #904)

- shift the implicit '.' to be part of the default prefix. This allows
  things like "-image myimages_00" to work as might be expected.

Feature processor level of detail (LOD)

See merge request OpenFOAM-plus!210

- respect trailing '-', '.', '_' for the image prefix name.
  For example,

    -image press_   to accept press_*.png

- additional -mask width option (for avconv)

- SIGFPE handling, cmake configuration

CONFIG: adjust for simplified Catalyst channel naming

- no sub-channels, select volField output based in the
  (internal | boundary) dictionary switches instead

- do not need the stringOps version if there is no dictionary context

- rename Allrun.parallel to Allrun-parallel (issue #899)