Fixed list-snapshot command
rb: Fixed broken Store#activateConfig
rb: Refactored Store#activate.

Store#activate now uses makeSnapshotWithOptions internally.
rb:  fixes to Node#identity_group.

Recent changes to Node#identity_group (viz., returning a group object
instead of a group name) introduced a crashing bug.  This commit
removes that bug.
rb:  first pass at Node#whatChanged
py:  first pass at Node#whatChanged
py: fixes to arc_utils
py:  group#membership
Various client-library fixes and missing methods.