This reverts commit c5bea524.

This reverts commit b18f6cc1.

ptscotch - compiles into ptscotchDecomp. All thirdparty decompositionMethods
now moved out of decompositionMethods so add them explicitly to link line
for programs that need them (decomposePar, snappyHexMesh etc.)

The dummyThirdParty tree builds libraries which are drop-in
(but non-functional) versions of some thirdparty libraries. This will
make it easier to ship binary versions without having to ship thirdparty packs.

The global sum of (integer) weights for metis&scotch has to be within the
valid range of integers. For now just divided the input (scalar) weights
with the minimum before truncating to integer.

Scotch is now built using its own build system which builds
an additional metis.h which conflicts with the metis one so
to have separate include directory settings we also need separate
Make/ structures.

- in preparation for adding an optional '-reconstruct' to a few utilities
  re-use as -lreconstruct library

- move related stuff there too
      src/decompositionMethods/decompositionMethods
      -> src/parallel/decompositionMethods

- added missing namespace qualifiers