- make warning optional and reuse in cellDistFuncs::getPatchIDs

STYLE: integrateLimits() -> integrate() for consistency with
  DataEntry/polynomial.  Rename old 'integrate', 'integrateMinus1'
  methods to 'integral', 'integralMinus1' (ie, substantive instead of
  verb for clarity).

Higher-order upwinded: Reorganised linearUpwind and created an equivalent quadraticUpwind scheme from it

- added canIntegrate flag - issues warning if false and debug flag set

With processorCyclics there can now be multiple interfaces between two processors