DOC: updated README and added missing Allwmake/Allwclean

Allwclean

+#!/bin/sh
+cd "${0%/*}" || exit                            # Run from this directory
+#------------------------------------------------------------------------------
+
+src/Allwclean
+
+#------------------------------------------------------------------------------

Allwmake

+#!/bin/sh
+cd "${0%/*}" || exit                            # Run from this directory
+#------------------------------------------------------------------------------
+
+src/Allwmake
+
+#------------------------------------------------------------------------------

README.md

-# external-solver
+# petsc4Foam
 
-Exploration and testing of linear solvers, matrix operations etc.
\ No newline at end of file
+## General Description
+
+Library for [OpenFOAM] that provides a solver for embedding [Petsc][Petsc]
+and its external dependencies (i.e. [Hypre][Hypre]) into arbitrary OpenFOAM simulations.
+
+The library provides:
+- ldu2csr matrix conversion.
+- selection of solvers and preconditioners available in [Petsc] 
+  and in its external libraries (i.e. [Hypre]).
+- editing of run-time options by a dictionary and/or a rc file.
+- basic caching implementation of a Petsc matrix.
+
+
+## Requirements
+
+1. [OpenFOAM-v1906] or higher or a recent [development version][OpenFOAM-git]
+   from [OpenFOAM.com][OpenFOAM].
+2. [Petsc] 3.10 or newer,
+   optionally compiled with [Hypre] support (optionally with MPI support).
+
+## Building
+
+Ensure that the OpenFOAM environment is active and that Petsc 
+can be found (check that the `PETSC_ARCH_PATH` environment variable is properly set).
+Read [How to build Petsc for OpenFOAM][Petsc-Installation] for more information
+or visit the Petsc website [How to build Petsc][Petsc-Ext-Installation]. 
+
+### To install in the normal OpenFOAM directories (using `wmake`)
+
+Simply use the supplied `Allwmake` script:
+````
+./Allwmake
+````
+This will install the library under
+`FOAM_SITE_LIBBIN`.
+
+
+## Authors
+
+- Mark Olesen | <mark.olesen@esi-group.com>  | (ESI-OpenCFD)
+- Simone Bna  | <simone.bna@cineca.it>       | (CINECA)
+
+
+## License:
+
+Licensed under GNU General Public License <http://www.gnu.org/licenses/>
+with the same terms as OpenFOAM itself.
+
+----
+
+[OpenFOAM]: https://www.openfoam.com
+[OpenFOAM-v1906]: https://www.openfoam.com/releases/openfoam-v1906/
+[OpenFOAM-git]: https://develop.openfoam.com/Development/openfoam
+
+[Hypre]: https://computing.llnl.gov/projects/hypre-scalable-linear-solvers-multigrid-methods
+[Petsc]: https://www.mcs.anl.gov/petsc/
+[Petsc-Installation]: etc/README.md
+[Petsc-Ext-Installation]: https://www.mcs.anl.gov/petsc/documentation/installation.html

src/Allwclean

+#!/bin/sh
+cd "${0%/*}" || exit                            # Run from this directory
+#------------------------------------------------------------------------------
+
+petsc/Allwclean
+
+#------------------------------------------------------------------------------

src/Allwmake

+#!/bin/sh
+cd "${0%/*}" || exit                            # Run from this directory
+#------------------------------------------------------------------------------
+
+petsc/Allwmake
+
+#------------------------------------------------------------------------------

src/petsc/Allwclean

+#!/bin/sh
+cd "${0%/*}" || exit                                # Run from this directory
+. ${WM_PROJECT_DIR:?}/wmake/scripts/wmakeFunctions  # The wmake functions
+# -----------------------------------------------------------------------------
+
+rm -f $FOAM_LIBBIN/libpetscFoam*                 # Cleanup library
+rm -f $FOAM_SITE_LIBBIN/libpetscFoam*            # ... extra safety
+rm -f $FOAM_USER_LIBBIN/libpetscFoam*            # ... extra safety
+
+# Cleanup generated files - remove entire top-level 
+removeObjectDir "$PWD"
+
+# -----------------------------------------------------------------------------