nodes now default to skeleton group membership
refactored setup_empty/1
paper-bag fix to app file
Ensure special groups exist.

All entity creation invocations through the internal Wallaroo API will
ensure that the skeleton and default groups are created.
Fix config-append prefix interpretation.

Config append prefixes may have been present in generated node configurations
when the initial append was to an empty value.  This commit fixes that.
added wallaby_config:reset/0
debug log improvements
Initial walk-in node support.

Walk-in nodes are now given the configuration of the skeleton
group applied atop the configuration of the default group.  Node
configurations will thus always be available when requested via
the internal API (and thus the REST API) for a valid commit.

This also switches cached node configurations to use the
lightweight format as in Wallaby classic.
Conditional skeleton group support.

Walk-in nodes now only get the skeleton group config if the
skeleton group is not disabled in the application configuration.