If a well is nominally connected in inactive cells, i.e., if its
connections have not been filtered down to the active connections
only, then 'allIndices' may not be a permutation of
0 .. allIndices.size()-1
Handle this case by sizing 'storageIndex_' according to the maximum
index value insted of 'allIndices.size()'.
This commit adds a new container class,
ParallelPAvgDynamicSourceData
which inherits from PAvgDynamicSourceData and provides a parallel
view of source contributions. Member function
collectLocalSources
will call the user-provided source term evaluation function for each
source location in its purview--typically those locations owned by
the current MPI rank. Those values will be distributed to other MPI
ranks through member function synchroniseSources which will fill the
base class' 'src_' data member, and become available to clients
through read-only item spans.
