Update logging and code comments in preparaion for continued refactoring.  Reinstate SubGroupValueMap.
All tests pass.
Next step: refactor FieldDescription to allow use of dynamically provided field list (from list description)
Working towards unified handling of repeated values across views and lists.
Currently reverted to old handling of lists, withj all tests passing.

The current problem is that the revised handling (using a repeat field renderer)
dramatically changes the internal context structure, breaking many tests.  Need to
rethink how to test list rendering (and more) without depending so much on internal
context structures.