using a run-time selectable preconditioner

References:
    Van der Vorst, H. A. (1992).
    Bi-CGSTAB: A fast and smoothly converging variant of Bi-CG
    for the solution of nonsymmetric linear systems.
    SIAM Journal on scientific and Statistical Computing, 13(2), 631-644.

    Barrett, R., Berry, M. W., Chan, T. F., Demmel, J., Donato, J.,
    Dongarra, J., Eijkhout, V., Pozo, R., Romine, C. & Van der Vorst, H.
    (1994).
    Templates for the solution of linear systems:
    building blocks for iterative methods
    (Vol. 43). Siam.

See also: https://en.wikipedia.org/wiki/Biconjugate_gradient_stabilized_method

Tests have shown that PBiCGStab with the DILU preconditioner is more
robust, reliable and shows faster convergence (~2x) than PBiCG with
DILU, in particular in parallel where PBiCG occasionally diverges.

This remarkable improvement over PBiCG prompted the update of all
tutorial cases currently using PBiCG to use PBiCGStab instead.  If any
issues arise with this update please report on Mantis: http://bugs.openfoam.org

Patch contributed by Mattijs Janssens
Resolves bug-report http://bugs.openfoam.org/view.php?id=2235

Patch contributed by Bruno Santos
Resolves bug-report http://bugs.openfoam.org/view.php?id=2233

This allows freedom in the naming of patches when patchGroup-based
boundary specification is not used.

Patch contributed by Mattijs Janssens

Resolves bug-report http://bugs.openfoam.org/view.php?id=2224

Patch contributed by Mattijs Janssens
Resolves bug-report http://bugs.openfoam.org/view.php?id=2227

Resolves bug-report http://bugs.openfoam.org/view.php?id=2225

Resolves bug-report http://bugs.openfoam.org/view.php?id=2223

This reverts commit 12ee0179.

If this clash is allowed boundary conditions set by wildcards are
processed incorrectly.

Patch contributed by Bruno Santos
Resolves bug-report http://bugs.openfoam.org/view.php?id=2218

  - There will be triangles rendered inside the mesh (when
    surface-rendering), because one of the cell's triangles is defined
    as a quadrangle in VTK_WEDGE.

  - Therefore, this VTK_WEDGE representation is only used when
    decomposing the mesh, otherwise the correct representation is done
    by VTK_POLYHEDRON.

  - Furthermore, using VTK_PYRAMID gave worse result, because it renders
    2 triangles inside the mesh for the collapsed quadrangle, likely due
    to mismatch with the adjacent cell's face.

  - Using VTK_HEXAHEDRON was not tested in this iteration, given that it
    should give even worse results, when compared to using VTK_PYRAMID.

Patch contributed by Bruno Santos
Resolves bug-report http://bugs.openfoam.org/view.php?id=2099

Patch contributed by Bruno Santos
Resolves bug-report http://bugs.openfoam.org/view.php?id=2216

Patch contributed by Bruno Santos
Resolves bug-report http://bugs.openfoam.org/view.php?id=2216

Resolves bug-report http://bugs.openfoam.org/view.php?id=2214

Patch contributed by Bruno Santos
Resolves bug-report http://bugs.openfoam.org/view.php?id=2213

Patch contributed by Timo Niemi
In response to bug-report http://bugs.openfoam.org/view.php?id=2199

Patch contributed by Bruno Santos
Resolves patch request http://bugs.openfoam.org/view.php?id=2212

  - "$FOAM_USER_APPBIN" and "$FOAM_USER_LIBBIN" have been added to
    "foamOldDirs" in "etc/bashrc" and "etc/config.sh/unset"

  - "$OPAL_PREFIX" is now undefined in the option "SYSTEMOPENMPI" within
    "etc/config.sh/mpi", but only if the path defined in this variable
    is cleaned when using "foamCleanPath".

  - "$OPAL_PREFIX" is now also conditionally undefined in
    "etc/config.sh/unset" when the path is picked up by "foamCleanPath".

Patch contributed by Bruno Santos
Resolved bug-report http://bugs.openfoam.org/view.php?id=2210

Patch contributed by Paul Edwards, Intel.

Patch contributed by Bruno Santos
Resolves bug-report http://bugs.openfoam.org/view.php?id=2207

Resolves bug-report http://bugs.openfoam.org/view.php?id=2194

Resolves bug-report http://bugs.openfoam.org/view.php?id=2203

Resolves warnings from clang

Resolves compilation failure with clang

Resolves bug-report http://bugs.openfoam.org/view.php?id=2182

Patch contributed by Bruno Santos
Resolves bug-report http://bugs.openfoam.org/view.php?id=2090

Contributed by Sergey Sindeev

viscosityModels::Casson: Updated constructor to avoid the need to specify the dimensions of the coefficients