Absolute enthalpy h = hs + hc.

- drop copy components constructors in favour of the xfer versions. Even if
  the caller sends through constant data, if will be automatically promoted
  to xfer (via a copy operation).

  - dropped non-const tmp::clear() in favour of the const version

- use xfer form for calls to resetPrimitives

  - keyedSurface is similar to triSurface, but uses faces
  - meshedSurface is sorted in regions and should be more memory efficient
  - surfMesh is the placeholder name for an OpenFOAM native surface format

  - send error messages to stderr
  - added -h/-help options where some were missing
  - changed 3-space to 4-space indentation
  - where possible, allow multiple directories from the command-line

Changed the quadratic scheme to quadraticLinear (linear in the plane of the face).
Added a linear scheme based on the CFC stencil used by the quadratic scheme.