Add DDS and AttrTable logging to FoDapCovJsonTransform functions

[hemphilc]

We can use the DDS class print functions to add logging to some of the transform functions so we can get a better idea of what a DDS object is as well as better understand the state of the object as it flows through the functions.

• DDS.h
• DDS.cc
• FoDapCovJsonTransform.cc

We can call the log file something like "FoDapCovJsonTransform.log".

[hemphilc]

Also printing for AttrTable objects:

• AttrTable.cc
• AttrTable.h

[hemphilc]

Should we still implement this, or just forget about it?

[hemphilc]

Validation class set up to validate attributes.