a generic table descriptor unit

Work on the basic interface is going well. I expect to do a first beta release tomorrow, after which I want to spend some time updating the documentation.

I am also considering the addition of a generic table descriptor unit to the CabinetDescriptorUnit and the DefaultDescriptorUnit. This then would allow for the creation of tables even using the basic interface, though without pre-defined columns. This would require an enhancement to the crc command implementation.

One concern here with ongoing enhancements is that rerunning crc might remove existing entries to the NewTopicNameMap in various DescriptorUnits. My thought here is to add some additional logic to merge the generated entries with existing ones. --A consideration that is important for administrators who are already defining their own DescriptorUnits, if not now, then in the future.