DWDS/Dialing Concordance Code

* 2018-08-17 added new command-line utility ddc_union
- based loosely on old ConcordUnion.cpp code (and the code it calls)
- ConcordUnion.cpp & friends supported only binary union operations, and no option-modification (e.g. MaxTokenCountInOnePeriod)
- new code supports n-ary union including option update and target attribute selection (via -O option)
- old code was apparently never called (and was broken in some places), and should probably go away now