Make avtUnstructuredDomainBoundaries.C better

[JustinPrivitera]

The code in avtUnstructuredDomainBoundaries.C is the stuff of nightmares.

• Quadruple pointer indirection int ****cellPoints;,
• variables that are declared and used for a bit before being used again for entirely different purposes (size_t nPts = givenPoints[index].size(); and then later nPts = idList->GetNumberOfIds(); in a loop),
• strange vector semantics givenPoints.resize(givenPoints.size() + 1);,
• redundancies int index = GetGivenIndex(fromDom, toDom); and a few lines later int sIndex = GetGivenIndex(fromDom, toDom);,
• poor choices #define ExchangeData_unsigned_char ExchangeData<unsigned char>,
• inconsistent operators nGainedPoints[sendDom][recvDom] += (int) nPts; versus nGainedTuples[sendDom][recvDom] = nTuples; (+= is wrong in this case)

Let's make it better.