Implement a node command controller

[remuslazar]

This implements a new "node command controller" to do things like:

$ flow help node:dump
Dump the content of a specific node
COMMAND:
  cron.neosclitools:node:dump
USAGE:
  ./flow node:dump [<options>]
OPTIONS:
  --url                URL of the node, e.g. '/news'
  --path               full path of the specific node, e.g.
                       '/sites/mysite/node..'
  --identifier         Node identifier, e.g.
                       30fb88f3-36da-49c4-9dee-2a16dd01bf78
  --workspace          workspace to use, e.g. 'user-admin', defaults to 'live'

And so to dump the content of a specific node as JSON.