[vnode parsing] Move core logic to j2

[vnode parsing] Move core logic to j2

j2/python is easier to read and manipulate strings, although it does
need some special care about undefined dict keys.

With this in place, deploy.sh only contains the higher level logic for
the deployment process.

- merge arch-specific default configuration files into a singular
  file with arch name as main dict key of old config (also avoids
  creating duplicate 'virtual' YAML keys in $LOCAL_PDF);
- move template handling to separate <lib_template.sh>;
- decouple tight bash ordering of scenario expansion -> parse_yaml ->
  variable export (e.g. CLUSTER_DOMAIN) -> re-use in cluster j2s;
  however we can't parse *all* j2s in one go, as scenario j2s might
  expand to YAMLs needed while expanding cluster j2;
- split `do_templates` into separate functions for each stage, with
  no coupling between them other then call order;

Change-Id: I4b5e804094c00e5e918caf769fd85fa52181ad76
Signed-off-by: Alexandru Avadanii <Alexandru.Avadanii@enea.com>