non constraint patchFields on constraint patch types (all fields)

ENH: change some iterator -> const_iterator access

BUG: found some places with forAllIter and ::iterator !

STYLE: use 'forAll(' NOT 'forAll (', as per coding guide

This change allows functionObjects to cleanly terminate the code e.g. on convergence.

Improves the handling of residuals from the segregated solution of vectors and tensors.

This data can be used for convergence testing e.g. by a functionObject.
Other data could also be stored, e.g. global continuity errors and other reduced results.

Exactly the same as processorGAMG versions

planes, rather than a vertex-by-vertex check.  Assesses concavity as
relevant to the tracking.

A cell is concave if there is a face whose face-centre is outside the plane of any other face on the cell.
Another option is to check for any vertices being         outside      ,,    ,,
but this is not consistent with current tracking.

Added compressibility support to MRFZone.
Required generalisation of the oneField concept.
Also clean-up the use of one and zero for consistency.
Simple mixerVessel2D tutorial case supplied.