Implement helpers to keep node ressources in sync

Worked on the lwrp sync_mark to enable chef to keep nodes in sync.
The lwrp sync_mark action :create will set a sync mark in the node attributes
(an identifier  and a mark) and save that mark on the server.

With the lwrp sync_marc action :wait a node will halt recipe execution until
a sync mark (identifier and a mark) will be set to mark-finished on all nodes
in the cluster. This works also if that particular mark has never been set on the node
where the action is run.

Also used the lwrp once in the default recipe
Issues:
  - Timeout is probably not working properly yet?
  - Does node_count always give the right numer of nodes?
  - resource.revision is not used atm, in general a cleanup is needed